Putin acts pretty rationally, just with flawed information. "Launching a full-scale invasion on the capital with the intention of negotiating neutrality" is a crazy plan he would never come up with. That's like beating someone up to get them to like you. The initial goal of the invasion was clearly to remove the democratically elected leadership of Ukraine, and then either incorporate it into Russia or (more likely) to install a puppet government that's more favorable of Russia.

On day 7, the three-day military excursion to Kyiv had stalled, the Russian army was scrambling to establish supply routes and figure out logistics for a war that should have been over, and Putin was trying to convert a stalemate into something he could call a success. Nobody at the time would have claimed that his behavior on day 7 was reflective of his plans on day 1, when days 3-7 were clearly not going his way.