Presumably the reasons for the initial attack still exist

Then… they failed? You’re saying that if they win, they fail. Or at least, they can’t win hard enough to actually get what they want.

Sorry, but I don't understand what you're trying to say here. If, for example, one reason for the initial attack was enlarging their area for more natural resources, why would they fail even if they win? It's incredibly naive to think their goal is something boolean, that you either achieve or don't. If your goal is to get more land, you can win once - and then invade again. How is this not obvious to you?

You’re also assuming Russia wants territory. If Russia wanted, say, Ukraine not being admitted to NATO, and they can get a peace that ensures that, then there isn’t a reason for them to invade again.

Then why didn't Russia make this offer after a couple of days? Why is Russia not indicating that this is any kind of option? They are the aggressor, they have the power to stop this, especially if they say what they want.

Or if Russia wanted UKR to stop shelling the eastern regions, then annexing just them might stop that, in which case, they don’t have any reason to invade again.

How in the world do you believe an invasion into a neighbouring country to reduce the likelihood of "shelling eastern regions"?