NO 2 NATO NEGOTIATION!

NATO never intended to make Ukraine a member. To much risk of being drawn into a war with Russia.
The US wants no direct war with Russia, to much risk of uncontrollable escalation.

The Russians think the US will make Ukraine a member and they worry about that outcome so much they will go to war to stop it.
They say as much to the US and NATO, they promise military intervention if formal security guarantees are not given.

So the US knowing as we do had little intentions of bringing Ukraine into NATO such a move has the same potentially uncontrollable escalation risk. The Russians really need to be assured of that formally, they have reconstituted themselves as a military power and demand an end to the military expansion so obviously directed at them.
Basically neither the US or Russia wanted Ukraine in NATO so why the war?
Well why not?
Works for the US, doesn't work for Russia, works least of all for Ukraine but hey, it's the US in driving seat. To get a nice safe proxy war with Russia all the US had to do in early 2022, was refuse to negotiate the basic and acceptable core Russian demand.