1) The US and Europe will dive in with a lot of jingoism at first, perhaps too aggressively threatening WWIII (the latter did not happen)
2) Some of the bigger psychopaths in the Blob will welcome a war of attrition that keeps Russia bogged down, whatever its impact on Ukraine
3) Barring an unlikely Ukraine "victory" or someone putting a bullet in Putin's brain, eventually the US and Europe would tire of the various costs (obvious and less obvious ones, the less obvious ones including some horrifyingly corrupt shit).
4) Ultimately some sort of peace will be achieved which will involve Ukraine giving up territory. The "conspiracy theory" version of this is that something much like this inevitable was on the table in the beginning, but was scuttled by UK and US Blob psychos.
WWIII didn't happen and the "conspiracy theory" is not necessarily true, but the rest of it basically is, even though I don't think the implications of that are especially clear.
The righteousness of a cause should not obscure the reality.