The territory is relatively easy to overrun with speed - the defensible choke point is on the wrong side of Ukraine (for the Ukrainians). It is only occupation that can prove to be difficult, or even intractable.

It's been 1 day, they're already in Kyiv and discussing surrender. I don't know the future, but it looks like the rest of the world had their pants down on this one so far, which seems surprising given the repeated warnings something was going down.

By the time there is a real response, it's looking like this may be over. Given that their urgency was "I'll talk to world leaders about what to do tomorrow" rather than "let's enact the plan we already prepared during the weeks of warnings" I think we know which way things are headed.