I can offer a rationale that I hope that will be interesting. Evidence is more effort than I'm willing to invest in a random internet conversation. I hope that's okay. I don't mean to cause offense, but neither do I like having an interesting discussion shutdown.

Executive leadership compensation tends to be based on, - the size/prospects/complexity of the company - the compensation received by executives in similar roles at other companies - the amount/type of oversight by the board

This incentivizes executives to increase the complexity of their role in order to justify greater remuneration. The classic example is turning a widget factory into a widget financial services provider. In this case, by behaving like Silicon Valley companies chasing the latest fad the executive leadership of Mozilla get to demand the same remuneration packages.