If Putin was going to invade with intent to conquer, he could have done it hard and fast and with as much surprise as he could manage. He did not do this because he would not be supported by the other authoritarian countries, and Russia would become the lone target for sanctions and political condemnations until Ukraine was released.
He either needs a legally-debatable reason to invade (fabricated or actual attacks by Ukraine, Ukraine murdering or expelling Russian sympathizers/nationalists from Ukraine, Ukraine's own uprising of Russian sympathizers/nationalists, etc) or he needs enough other countries to form a "military coalition of authoritarians" (as happened before many times before in history), so that group of nations can physically express their desires to conquer/enslave/exterminate anyone they want to.
This is the large scale version of "attempting to flush game when you are hunting"... You use loud and startling provocations to get your target to start running so you can justify shooting it. That is the core of it... for police who seek excuses to use force, for "militia" civilians who seek excuses to use force, for tavern-hoppers who seek to use force, for 7 year-olds who seek excuses to use force. There is a mental drug release when you succeed in flushing a target into the open, and the "thrill of the chase" is a result of that mental drug release.
Putin is not posturing or sabre-rattling, he is hunting...
His focus on getting authoritarian leaders into power in other countries is part of this. That mental drug release has another feature, it blinds the hunter to the ethical and moral considerations of the situation. It blinds the hunter to the consideration of "am I killing to survive, or am I killing for the joy of killing?"
Putin is hunting... and he wants others to join him.