John Harbaugh apparently only gave Jim a DC for a year, and has decided that because he had to let his DC go, it was time he take his brothers intern back. This could be difficult to navigate, and could be a determining factor on Harbaugh staying or going (if he were offered a NFL job which is looking less likely).
[Mod edit - closing. More discussion on this topic here: https://www.elevenwarriors.com/forum/college-sports/2022/01/128957/ttun-dc-mike-macdonald-expected-to-take-ravens-dc-position]