1. Russia has gas over Germany.
2. Amassing troops on Russia's boarder without an alliance with Ukraine is politically challenging.
3. America is sick of war and doesn't have a good looking balance sheet.
4. China is the new meta. Taiwan is tough enough.
5. Joining Nato is a process starts with have a certain level of democratic freedom and market economy that Ukraine is in the process of attaining. If we defend them right now, then it undermines the reforms we want them to make before joining. Once they're in, they're our problem.
6. Covid and knock-on effects is still the focus.
Doesn't mean I love it, but it's the reality. Personally I'd do things differently, but I don't exactly have presidential intelligence reports now do I?