It's because they're bankrupt and that's what happens to bad banks.
One of the proudest names in English soccer will, essentially, be bankrupt.
Unfortunately, using stock price as a proxy for company performance is a bankrupt idea.
1560s, from Italian banca rotta, literally "a broken bench," from banca "moneylender's shop," literally "bench" (see bank (n.1)) + rotta "broken, defeated, interrupted" from (and remodeled on) Latin rupta, fem. past participle of rumpere "to break" (see rupture (n.)). "[S]o called from the habit of breaking the bench of bankrupts" [Klein]. Earlier in English as a noun, "bankrupt person" (1530s).
1550s, from bankrupt (adj.). Related: Bankrupted; bankrupting.