There are about 3500 billionaires in the world, meaning they emit as much CO2 in total as roughly 3.5 billlion people from the bottom 90%. They do play a huge part in this.
A quick google search indicates that the top 1% accouted for 16% of greenhouse gas emissions. https://www.oxfam.org/en/press-releases/richest-1-emit-much-... Yes that is a lot. But 1% includes many more thn just the billionaires and it also means that if the remaining 99% don't get their emissions in check, it doesn't matter much what the top 1% do, let alone the billionaires.
Don't get me wrong, I'm not saying the billionaires should not do anything. If anybody is in a position to adjust their behavior, it's them. But acting as if as long as the billionaires don't change their behavior, nobody needs to, is the route straight to failure, though it is a very easy narrative for sure.
8.3bn people on earth. 90% if that is ... more than 3.5bn? Something like 7.4bn? How can "the bottom 90%" be included in those 3.5bn?
And I also don't follow where the "a million people in the bottom 90%" are suddenly coming from. Which million out if those 7.4bn people?
I'm really at a loss w.r.t. your arguments.