I'm not an expert but I don't think Russia wants the whole of Ukraine, never did. But may be forced cancel Ukraine as a country. They could have canceled the state at any time I think, just bomb Zelensky and all the politicians. Probably some fear of a WWIII too if they go too aggressive. So they hope for a settlement that seems secure and lasting but it seems impossible to me at this point. So more military destruction it is then. Trump was on board with the Russians at Anchorage, saying "ceasefires typically don't last" but has vacillated every way since then.
That was the original plan at least, when they tried to take Kiev, to control the government and then possibly incorporate the territory into Russia.
Concerning the peace deal, possibly could end with the current areas of control with a DMZ zone. Russia is also trying to bargain for extra territory which they haven't taken, though Ukraine would of course not accept this.
Could also be delaying tactics as used by North Vietnam where the 'negotiations' are a sham and a form of delaying tactics.
Either way, a peace deal with the current borders saves face for both sides:
Russia says they took the Russian-speaking areas.
Ukraine says they stopped Russia taking control of the entire country and government.
The map has barely changed:
