The Russian army is currently approx. 640,000 men in Ukraine sub-divided into 3 sections: Frontline, Reserves, and Rear-area training and rebuilding. It is really not a big army to occupy a 1,300 kilometer frontline.
Europe has vast manpower superiority over Russia and could easily supply all the infantry Ukraine would need if there were, say, over 1 million men willing to fight for Ukraine. But they are 3 years too late and it looks like Europeans do not have the stomach to fight in any type of war.
Putin has accomplished perhaps 80% of his minimalist territorial goals (annexed in 2022) and managed to do this without rebuilding the Soviet Army, without mobilizing more reservists and causing a threat to his dictatorship. It seems that once he appointed an economist and his staff as defense minister they went for a strategy of recruiting contract troops with very generous benefits (like the US, if not relatively more) that would propel people willing to risk their lives into the Russian middle class.
It seems that the war in a current negotiated settlement would end up with Ukraine being reduced into a base-ball shaped sized country with the south/east in Russia hands. And it is more likely than not that a restart of hostilities will happen some time down the line.
And it would require the 'de-militarization' of Ukraine which is a non-starter for NATO. That is also a minimalist goal for Putin and he can't walk away from this war without disarming the Ukrainian ground force. And Ukraine's high demands in exchange for their massive sacrifices make negotiation very difficult.
There is a possibility that Trump will fail and the Russians would just continue grinding the frontlines with artillery & drone warfare everyday for years if need be until Ukraine surrenders to their minimalist goals.