Shoigu's role as defense minister was widely seen as untenable after one of his key allies was imprisoned on corruption charges and Shoigu was seen as not having done enough to root out the problem. This move allows Putin to get rid of him while allowing Shoigu to save face so he doesn't later become an issue.
With Russia moving to a war economy, with a large percentage of gross domestic product going towards military expenditure, it's important to have an experienced economist heading the defense ministry so that national spending is streamlined — but also innovative — so that progress continues to move forward.
There's a 50% chance that Vladimir Putin will cease to hold the office of president of Russia by February 2029, according to the Metaculus prediction community.