The US invaded on March 20th. Iraq's head of state was captured on April 9th.
Russia isn't even close to having the same problems that America encountered after its obscenely successful invasion. When/if they do actually have to occupy Ukraine and sustain insurgency, it's going to be an absolute nightmare for decades.
Russia mustered all the might it could in an attempted shock and awe campaign against Kiev, the problem is that Russia is a 3rd world country that acts like it's not because it 1) used to be a 3rd world empire and 2) it has nukes. Russia and its military have been thoroughly gutted by decades of kleptocracy.
Largely out of the entirely unsupported belief, which you seem to share, that Putin could easily unleash huge reserves of untapped offensive potential any moment he wanted to (aside from nukes, which are of course completely useless for what he's trying to do in Ukraine).
The simple fact is, though, he just doesn't have that capacity. If he had it, he would have certainly made use of it by now, now nearly 3 years in. It's simply preposterous to suggest he's sitting on some massive potential, but hasn't been using it yet for some mysterious reason.
Guys... he's just a dictator like all the others through history: fundamentally confused by an information environment of his own making, undermined by systemic corruption and a culture of distrust, and dangerously delusional in his ambitions.
He's just a complete loser, and his clowncar of an invasion is an extension of that fundamental loserness.
The US has always had to contend with the risk of coming up too hard and collapsing Russia. No one wants rogue generals with nuclear armed ICMB.
Putin’s 15th degree of chess is where it all is revealed as strategic genius.