Do you have a reason to believe they already knew it was toxic? (If you meant me, I don't work or worked for apple). If you read the thread, they had significant investment in apple making it hard for them to leave.
Of course, the same could be said of other large corporations.
Further I’d suggest if you’re an engineer where only one company in the world can employ you, and you’re not getting fuck you money from it, you’ve done it wrong.