I’m assuming the West’s analysis is that there’s no better political reality inside Russia in sight, even with Putin gone, so they’re better off just declawing the bear. Which to a large degree has already happened…
Meanwhile the upside is that the collective West gets to try tactics and weapons for modern warfare (drones, ai, analysis) and get ready for the next fight. They also gained a fight-ready, trained ally in Ukraine and a sharper focus in Europe of what’s at stake and everything that that involves (eg energy and supply chain independence).
The downside is obviously the deaths of Ukrainians in the front line, but I don’t know how many of them could be prevented without NATO getting properly involved.