Sirsky is replaced with Mikhail Drapatyi after protests demanded the old commander-in-chief gone, after Def.Min. Fedorov was sacked. Zelensky offered a new place for the latter in the govt., people like him.
I heard Drapaty is a "new type of general". He is major general which is low rank. Since military reform was the issue between Fedorov and Sirsky we either might expect changes from Drapatyi (since he is young) or he will has the role to keep on to the line Sirsky held, he just an acceptable figure.
https://www.kyivpost.com/post/80782