I'll have to look again at sources but a lot of people have been talking about that on the grad over the last year or so.

IIRC Russian communists wanted to intervene in 2014 already, as they knew the conditions in Donbas would only worsen as the fascist Ukrainian regime only got stronger. These Russian internal political tensions finally boiled over and forced Putin to make a move in February 2022 when all even nominally oppositional media was banned in Ukraine. It was then that Putin and the rest of the liberals at the top of the Russian government were finally convinced that the situation in Ukraine for whoever the government determined to be non-Ukranians could only get worse without outside help. It also looked like an all out attack against the residents of Donbas was imminent.