A detail that may be surprising to many is that Lord Caitanya Mahaprabhu accepted sannyasa from Keśava Bhāratī, who is in turn part of the Bhāratī Mayavada school. In other words, Mahaprabhu is, formally speaking, a member of the Mayavada school. How can it be?
The point is that great acaryas usually uphold the principle that we should accept a spiritual master. Therefore, when they come they accept initiation from whatever school has some connection to the authentic parampara (even if their practices may have degraded over time) and from there propagate the proper philosophy of Krsna Consciousness.
Therefore, when Mahaprabhu decided to take Sannyasa, he thought it proper to take it from the school that was still practicing it, which was coincidentally the Mayavada school. These were also the sannyasis who were respected in society, which probably also weighed on the decision. Naturally, Keśava Bhāratī is actually Sandipani Muni, the Lord’s eternal guru, but still, the significance is there. Previously, Sandipani Muni offered the sacred thread to Kṛṣṇa and Balarāma and came to join the Mayavada school specifically to give initiation to the Lord.
In Teachings of Lord Caitanya (ch. 17), Prabhupada wrote: “They were surprised to see Lord Caitanya chanting and dancing after He accepted His sannyāsa order from Keśava Bhāratī, for Keśava Bhāratī belonged to the Māyāvādī school. Since Lord Caitanya therefore also belonged to the Māyāvādī sect of sannyāsīs, the Māyāvādīs were surprised to see Him engaged in chanting and dancing instead of hearing or reading the Vedānta-sūtras, as is the custom. The Māyāvādī philosophers are very fond of the Vedānta, and they misinterpret it in their own way. Misunderstanding their own position, they criticized Lord Caitanya as an unauthorized sannyāsī, arguing that because He was a sentimentalist He was not actually a bona fide sannyāsī.”
We can see that lord Caitanya accepted sannyasa in the Mayavada school and was practicing the basic sannyasa regulations, but He disagreed on other points, challenging their philosophy of oneness and propagating congregational chanting instead of the solitary study of the Vedanta Sutra. This made other Mayavadi sannyasis uncomfortable, to say the least, leading many to start to openly criticize the Lord.
Eventually, this led to Mahaprabhu meeting with Prakāśānanda Sarasvatī and converting most of the sannyasis through His personal qualities and His explanations of the philosophy of Krsna Consciousness. Not all Mayavadi Sannyasis agreed to follow Caitanya Mahaprabhu (that’s why the Mayavada school still exists), but many saw the light, so to speak.
Similarly, Srila Bhaktivinoda Thakura took diksha initiation from Bipin Bihari Goswami, who was technically a caste goswami. By that time they had philosophical inconsistencies and some of their practices were not exactly ideal, but that was a school that was connected with Srila Nityananda Prabhu and Jahnavi Devi. Therefore, the Lord guided him from inside his heart to take initiation from this school.
However, just as Mahaprabhu changed certain practices of the Mayavada school and propagated a different philosophy, Srila Bhaktivinoda Thakura propagated a reformed version of the Vaishnava philosophy, correcting philosophical misunderstandings and offering a different way to practice Krsna Consciousness. We can see that he simultaneously instructed new people through his nama-hatta program and most of his books, and simultaneously tried to create a bridge to attract people from the Goswami lines by writing books like Harinama Cintamani. This new philosophical line was perfectly represented by Srila Bhaktisiddhanta Sarasvati Thakura, who went further in reforming the sankirtan movement and transforming it into a dynamic process that can effectively help people from all ways of life into going all the way up to pure devotional service.
Srila Bhaktisiddhanta Sarasvati Thakura implemented several reforms, like the acceptance of the Sannyasa order (most Vaishnavas at the time were Babajis), he denounced the process of imagining oneself as a gopi or other personal associate (which was largely practiced at the time) as unbonafide and instead offered a practical process based on chanting, serving and hearing the scriptures. Most Vaishnavas at the time were found of solitary meditation, which he also deprecated, offering instead the dynamic propagation of Krsna Consciousness as a process of spiritual practice in itself.
Many up to this day disagree with these changes and consider them unbonafide. However, we can see from the results that such modifications were not only correct but necessary to break with the mistakes and deviations of the past and bring Vaishnavism back to its proper form. Many sincere Vaishnavas from the different schools present at the time joined Srila Bhaktisiddhanta Sarasvati and assisted him in his mission, while others rejected him and continued with their previous practices. These are still present and can be noticed even here in the cyberspace.
Similarly, after Srila Bhaktisiddhanta Sarasvati Thakura passed away, the movement he initiated passed through certain difficulties, which led to Srila Prabhupada trying to fix it by creating his own society. We can see that as time passes, different branches of different schools deviate in different degrees, and great acaryas come in succession to gradually restore the proper teachings. This process happened in the past with Lord Buddha, Shankaracharya, and Madhvacharya, who gradually rescued society from the depths of atheism, and continued in the modern age with Srila Bhaktivinoda Thakura, Srila Bhaktisiddhanta Sarasvati Thakura, and Srila Prabhupada, giving shelter to sincere Vaishnavas who want to reach the ultimate goal.
Regular human beings are not in contact with the transcendental are are thus not capable of introducing anything better than what is propagated by the previous acaryas. We are thus advised to just follow the parampara and not introduce changes, since all changes will inevitably lead to some form of degradation. We can see that our own movement is now considerably different from what Prabhupada established, with different practices that are not completely bonafide creeping in. This happened in the past and will continue happening in the future. We can’t revert this process, but we can try to at least slow it down by not introducing further changes. At the same time, we can appreciate the work of empowered acaryas who come from the spiritual world to periodically rectify things and put the sankirtan movement back on track.
Every time this happens, sincere souls are able to recognize them and move back to the proper path, while others accuse them of being unbonafide. It happened in the past and it will continue in the future. All we can do is to try to remain on the proper path, following in the footsteps of such empowered souls.