Sure. But that buffer was about to join NATO. Ukraine received a guaranteed invitation, so it is only a question of when, not if. Invading Ukraine pushes that, basically inevitable, NATO border further to the West.

> But that buffer was about to join NATO.

That is not correct afaik.

Besides that the downsides associated with all this far outweigh the upside of where NATO's borders are.

According to Wikipedia, both Ukraine and Georgia, received invitations. Ukraine is on an Individual Partnership Action Plan (English wiki, the German says something about guaranteed invitations...). So it seems both countries have been on aclear path to membership, Ukraine at least until 2014 when Obama said they were, in fact, not. In 2019 Ukraine amended the constitution with "goal" (facilitation, prerequesites,... didn't have time to research that) of both, EU and Nato, mambership down the line. Considering the necessary military build up to pull the invasion of, and assuming such an invasion to be impossible one Ukraine is either part of the EU or NATO, "about to" seems not to far of the mark. Especially for someone playing the long game like Putin.

Usual disclaimer, I don't consider any of the above a valid reason to start a war ot interfere in othet countries.