Sometimes tech companies have the wrong people at C-level. These people constantly make bad decisions, and have their subordinates pay for them.

Investors are often oblivious to these details. If the company is not doing as well as expected due to crippling tech debt, high turnover rates, dumb decisions, etc. the CEO will come up with an excuse (since COVID, this is easier than ever).

Because they drank the kool-aid that joins are bad (so implement them in your application instead!)....oops, mongo has joins now. It's still trash.

Because they don't understand RDBMSes and how to turn them for performance and have bought into cargo cult thinking.