Milan has been unlucky selling a club onto dodgy new owners on more than one occasion.
https://www.espn.co.uk/football/story/_/id/37403497/portsmouth-looking-long-slide-bottom
One thing the regulator should enforce is clubs can't put up season tickets for sale until March at the earliest. It's money for the following season, not to financially help a club mid-way through the current season.
Four of the bottom six teams are currently or just recently in receipt of parachute payments. Then there's Sunderland in league one, so plenty of teams squander them and fail to go up.