the rot sets in
The situation deteriorates. When you start charging everything to credit cards, that's when the rot sets in, and you've dug a hole too big to get out of. It's clear that the management isn't trying to retain this as a viable business. The rot has set in for sure.
the rot sets in
a rapid succession of (usually unaccountable) failures begins.the rot sets ˈin
a situation starts to get worse: The rot really set in when the team’s best player left the club last year.