If someone takes a "leave of absence" that ends up lasting several months, and that becomes a permanent leave of absence (read: they quit), that does indicate problems. Not in a one-off scenario, but in Tesla's case where they've lost dozens of executives once they realized that [possible bias here] Tesla is clearly engaging in fraud, it's not just a one-off thing. The smart executives are jumping ship, leaving behind either a) the not so smart executives or b) the smart people like Straubel who are close enough to Elon that they wouldn't leave.
see: bogus solarcity acquisition to avoid the dominos falling in Musk's highly coupled empire, clear intent to cause a short squeeze with the bullshit going private tweet [if you look at musk's actions/statements leading up to that, it's clear the shorts have been stressing him out], Musk having borrowed money to purchase even more Tesla shares, worker injury rate [this isn't fraud but I decided to throw it in there], etc etc etc