It's not any specific playstyle demographic that's keeping Kyurem, for example SupaGmoney arguably the best stall main was very adamantly pro Kyurem. The reason why a Kingambit suspect is not worth the effort to push / won't work is because majority of the playerbase believes it's necessary at this point. Whether that's true or not can be debated, but a very large amount of players of all levels of skill are afraid of the possible consequences of a Kingambit ban as well as how that'd effect teambuilding. Again whether this is warranted or even true, does not matter, in the nature of a suspect test it all depends on what's most likely the community is able to agree upon. Kingambit and Gliscor (with Kyurem) I just can't see ever crossing 60%+ ban rate in my opinion.You forgot the hidden 5th option, suspect Kingambit, which even players such as Storm Zone might vote ban on unlike with Kyurem. Kingambit is more toxic in design than Kyurem is 'cause of Supreme Overlord packed with ridiculous priority for a mon with that much natural bulk, and while there are players who want Kingambit to stay no matter what, I believe there's a chance offense players who repeatedly save Kyurem time after time again might be willing to punt Kingambit out of the tier.
Meanwhile Tera Blast maybe if we as a community advocate hard for it knowing that there's no other option. Part of why I am more confident on Tera Blast being potentially bannable via a suspect test, is because it's a blank slate. There's no die hard Tera Blast defenders so to speak, no one besides a few even have strong feelings torwards it. If we as a community can advocate for it and have people listen, people who are largely unbiased torwards the moves as of right now, we have a chance to make positive change.