They didnt. They borrowed heavily and spent over $800m on their stadium redevelopment, but were still making a profit throughout the pandemic despite seeing their revenues fall by 300m euros. During that time they were still able to reduce their debt on the playing side to about 34m euros down from about 200m.
Last year they signed a deal with a US company, Sixth Street, to use the Bernabau stadium for ‘Legends’ events which they get paid something like $500m a year I think. Just a couple of days ago they signed another deal with the same company for 360m euros allowing sixth street to run businesses from the stadium.
The stadium is due to be finished this year and expected to generate an additional 120m euros a year for the club. Then as said above there are several high earners who have left the club over the last couple of seasons or will be this summer.