Not Europe but a few Baltic states are feasible. No one says they can hold it, but Putin has his own reasons so we should not think we can conclude on future Russian actions based on what we consider reasonable - e.g. no one predicted that a war on Ukraine was likely as it seemed to be completely irrational and self-defeating.
If nothing else, war has been many times convenient to keep regimes in power (see Bush post 9/11 for an obvious example). Putin might want to strengthen his case. See absurd discussions / push for a "Republic of Narva" as an example cause belli.
“The West is leading Ukraine down the primrose path,” Mearsheimer averred in 2015, “and the end result is that Ukraine is going to get wrecked.”
https://www.nytimes.com/2022/03/09/opinion/ukraine-russia-in...
A sect of realpolitik theorists outlined why Russia would be compelled to invade Ukraine. Even Kissinger thought that expansion of NATO westward would compel war with Russia. To say no one predicted this or that it’s self-defeating for Russia is a mistake of analysis. The war logically follows from Russia’s security goals.
May sound like nitpicking, but the Baltic states are Europe both geographically and organizationally (eg members of the EU).