This crazy old poopy pants manchild is serious in that he wants to blackmail people into giving him something for nothing. Thankfully, he's so fucking stupid, and has created a cesspool of asskissers around him who are incentivized to suck up rather than actually DO anything.
He talks, says a lot of crazy shit, then backs down, having done damage and not actually gotten anything. Like being in a shortbus with a hormonal chimp with a chainsaw. We're all just going to have to wait until his inevitable toilet stroke, and then watch the whole thing collapse.
He works for the Russians, always has, these jackoff tarriffs which only seem to be against allies is meant to disrupt the focus on Ukraine's backers and force an immediate settlement where Ukraine only makes any concessions. It's clear as goddamned mid-day sun that everything he's doing is to unsettle NATO and get a win for Russia.
That proves several things, including his overall allegiances. It also suggests that Russia is truly desperate, doesn't think they will get more Ukrainian land than they currently have, and want to freeze the conflict to call it a victory. The current strategy of thrusting small infantry squads anywhere you can fit them isn't exactly a solid occupation strategy. Ukraine can kill many more of them, eventually, with drones, snipers, artillery, and counter-assaults. There isn't a baked in guarantee that they're allowed to keep all the stolen land they're sitting on right now. Ukraine will kill most of them - eventually - and he'll be left with nothing but a bleeding wound as his army tries to do the harder piece of warfare - pacification.
It's in Ukraine's long term interests to keep killing the Russian army as long as it can sustain it's own losses.