It isn't relevant in regards to why they were de-platformed, but if you want to look there are plenty more with higher view counts.

My understanding is that Apple wanted some form of auto-moderation. Parler's self regulation by user votes is a joke and leads to the opposite of free speech. They wanted a plan and a conversation, Parler refused. So, bye bye.

Apparently everyone has abandoned them, including their own lawyers. They could have fixed this, but they decided not to, and are now crying foul.