There are reports of captured Russian war plans. Im not sure where i read about it but War on the Rocks and Michael Kofman are credible experts.
I dont actually remember the details of the plan but It was something like:
Massive armor convoy sent to Kyiv alongside the rapid capture of Hostomel airport and a then a giant airlift of troops towards a point very much close to Kyiv.
The disdain the commenter is showing for the Russian invasion plan is misplaced however. Most contemporary reports (Post battle of Kyiv) say that the Ukrainians were indeed caught by surprise, that Russian cyberwarfare managed to take out Ukrainian AA allowing for the helicopter Assault at Hostomel and that although Ukraine was sucessful It was a close call and losses were heavy.
Again you have to Dig a bit to avoid the propaganda narratives. The race to Kyiv was actually a Very Very close battle according to what we know now.
The whole 3 days to Kyiv was actually an overstatement. I believe it was more 13 days to capture Kyiv, 2-3 months for the whole country excluding the West which Russia didnt believe It could occupy without heavy resistance. But thats just written out from memory and i might be wrong on the details.
I believe that the Russian expectation was something similar to 2014, where initial Ukrainian resistance just collapsed or was innefective.