They wanted to stay in Afghanistan even after 20 years but 2 years of Ukraine is too much.

People just keep parroting this nonsense about money being allocated to Ukraine being the problem when the actual problem is lack of industrial capacity in the west to produce weapons and ammunition at the rate they're being consumed. The west has now largely run through the existing stockpiles, and lacks the capacity to produce more in time. Mainstream western media now openly admits this https://www.theguardian.com/world/2024/feb/15/rate-of-russian-military-production-worries-european-war-planners

Allocating more funds for Ukraine isn't magically going to make stuff like artillery shells appear out of thin air.

This is how proxy wars go. The Republicans aren't bought out by Russia. The USA uses proxies for specific strategic goals. When the goal is achieved or becomes untenable, they cut off the proxy. That's just how it goes.

To avoid showing voters the realpolitik they need some plausible reasons for cutting off the proxy. Usually it's a combination of fiscal responsibility noise and isolationist noise. This is no different.

The USA was provoking Russia. Russia got provoked. The USA activated some sleeper cells, those cells got neutralized. The USA wanted to see Russian capabilities, they got what they could, including intel on hypersonic missile performance, but I don't know if they got what they wanted.

And then multiple fronts got opened up against the West (Niger, Palestine, etc) and threat escalations emerged in unexpected locations (Iranian missiles im Venezuela). And it's become clear the West can't produce the war machine it needs for the conflicts that are coming. So, it's time to cut off the proxy. Russia doesn't have the means to occupy Ukraine. The USA is not worried about Russian expansion, so there's no more reason to be there, except of course the rhetorical reasons that were used to mask the proxy nature of the conflict in the first place (russophobia, anti-communism, moral posturing, etc). So, to control the domestic mood, the Republicans get to play their part as dirt bags, make a bunch of rhetorical noise about why we can't fund them anymore, and psyops adds some Russiagate flavor through networks of influence to mask the reality: the proxy has outlived its usefulness and the USA is cutting them off.