I try not to give too much credit or blame on who the President is at anytime, in most cases they only move the needle a little bit in the big picture................BUT, I do believe this would not be happening if the Orange guy was still President. It might have be pushed out a few more years, maybe.
Facts are, Putin doesn't want a Western Like European Country next to his border, and especially a Nato member. Ukraine was starting to look more like Germany in terms of social/political standpoint. Now put in the equation all the natural resources Ukraine has and he also sees a piece of land that would make Russia a bigger player in their GDP. Currently Russia is nothing more than a large gas station, in the big picture this is the biggest thing they export.
Now take Biden and our country (and Nato), I don't think we have the balls to go in and fight this with the military. Biden as already said he would not send troops into Ukraine.
I think in the big picture, we have to hope the Russian people continue to protest Putin and these actions in his own country. Putin cares a lot about what his image is within his country.
Lets hope this plays out quickly, we really haven't seen anything like this since WW2.