Thanks for clarifying. That said the impression I got at the time is that his motivation to leave appeared closely tied to controversy around his past donations and personal beliefs. Hence the "under present circumstances" statement.
No problem -- it's a common misconception which is a key part of the narrative that Brendan's Alt-Right GamerGate supporters were doing their best to spread at the time (GamerGate was in full swing when he resigned, and the Alt-Right jumped on the issue at the expense of Mozilla), in order to help Brendan play the victim (instead of respecting Brendan's own victims and co-workers whose marriages he wanted to terminate) and make him a martyr. (Not that I think you're one of them, but they unfortunately succeeded at spreading the misconception that Brendan was fired far and wide, in the service of their cultural war.)