I don't know where this is coming from.
There were lots and lots of Naga boys in my Sainik School. Ours was their school of choice before the schools in Odisha and Assam opened up. Ever since then, the political establishment in Nagaland has always had a certain number of our students in positions of power.
There was never a Hindu population in Nagaland. In Censuses in the past, the animist population was counted under Hindu. Over time, many - most - of them have converted to Christianity, to the Baptist Church, mainly. That is why you will find the number of 'Hindus' dwindling, and the percentage of Christians steadily rising.
Only in Manipur is there a Hindu population, because the Meitei converted en masse in, I think, not sure, the 17th century, converted by a Gaudiya Vaishnav. The Manipuri dance and Ras Leela and those features come from that conversion.
Please take this on board. There is NO Hindu population outside Assam (not Bodoland, they are also not Hindu) and including Cachar in Assam.
You can check with
@brational, who is Assamese.