When Ukraine was flirting with the idea of a relationship with the EU in 2013-2014 the Crimean invasion happened. It was absolutely predictable even at that time and in fact many EU officials I have spoken to (including high ranking ones) agreed as much since back then. The signs of a regime which doesn't stand any proximity of a threat to their rule was obvious.
> The reason for the conflict is entirely in Putin's head
I have never been in Putin's head, nor met or talked to him. But to my pride I do forget more history every day than most people will learn in their lifetime and can't think of similar example of a superpower happily accepting adversaries at their border.
In recent history look no further than when the US ordered a naval blockade on Cuba after Cuba's request for Russian missiles to be placed on the island to defend in the event of another US invasion attempt. Putin is literally taking a page from that book.
I don't need to be in Putin's head because he's not some brilliant tactician doing something unheard of, he's just playing an old song to a new audience. If it's the first time you hear it you just have to pay more attention to what came before today.