Because it's very clearly not about GitHub and branch names - it's the ongoing thing with Pedro Domingos.
If you don't know, best to not just guess especially when it's a contentious subject where people are already clearly super frought. That's probably why you got down-voted heavily.
But if it becomes the default for the 56 million GitHub developers, is it really freedom of speech?
I don't disagree with renaming the default branch and I've been using the name develop as the default branch for 2 years now, but I am still not sure that changing it globally on a global platform qualifies as "good behaviour".
Edit:
If you disagree, can you please write a comment stating why you do?
It would be very helpful, if I am saying something obviously wrong I would love to understand why.
Thanks!