If we do, their demands will only get bigger and more extreme. It also incentivizes countries to pursue the nuclear get-out-of-jail free card.
Allowing Putin to continue to operate this way brings us closer to the day that someone will be forced to take a stand, or two unchecked nuclear rouge states end up at odds, and the likelihood of a nuclear confrontation will continue to increase until it becomes inevitable.
Furthermore, a proper NATO contribution to Ukraine would give Putin an excuse for losing, and allow him to save face by blaming The West (which he and his people are pretty used to). By contrast, a Ukrainian victory (possible, or even likely unless NATO steps in on Putin’s behalf and pressures Ukraine to surrender) would be humiliating in the extreme, and result in the total loss of all of Russia’s political capital, even in the eyes of MAGAs.
All of the same things apply here in the US. Refusing to confront Trump and the MAGAs has always strengthened him. He does outlandish shit, and everyone—from the Democratic Party to the Courts—is afraid to confront him. This is not only central to his appeal, it’s the very beating heart of his cult.
Everyone is afraid that trying to fight back risks a Constitutional Crisis if we lose. Instead, we’re content to dismantle the Constitution, and give Trump absolute power.