Are they drunk over there?
Whatever is causing them to turn around and want to hire him again is evidence he was underpaid. Maybe he’s got dirt on them, maybe they realized he’s actual crucial to operations. Either way, the negotiating field has changed now that they’ve revealed their desperation.
I mean the guy was easily making gobs of money. I don’t think he needs anymore money. Did he make less than others? Maybe. But he wasn’t at the bread bank looking for handouts.
Not really commenting on whether Altman got paid enough or not, but “well he’s not fucking homeless” isn’t really a sensible argument in any conversation about compensation.