Why did Dr. BR Ambedkar convert to buddhism?
i think Wikipedia articles on the man and on the Dalit emancipation movement give some insight into his reasons

https://en.wikipedia.org/wiki/B._R._Ambedkar#Conversion_to_Buddhism
https://en.wikipedia.org/wiki/Dalit_Buddhist_movement#B._R._Ambedkar

they appear to be primarily socio-political rather than existential and spiritual