You could argue that he shouldn't have caved.
Did he? My understanding was that the engineering manager in question was Allan MacDonald, and he refused to sign off on flight. The decision was taken out of his hands and authorisation signed by a non-engineering manager above him?
As a Chartered Engineer I have signed up to a code of professional ethics which says I would refuse and resign in such circumstances - I can only hope that if I ever find myself in that position I would have the integrity to put my family into dire economic straights and resign. I tell myself I would, but I've never asked myself to prove it...
As a fellow Chartered Engineer, working for much of my adult life in airworthiness, I've been too damned close too often. The fact is I have made both grounding, and non-grounding decisions a number of times, and every one of them has lost me sleep. To date, none have lost any lives - I hope that was my good judgement, it might have been my good luck. I recall one occasion where corporate pressure had me arguing vehemently against a grounding versus a CAA team, going home, thinking on it through dinner, and then logging in and emailing them "dammit, you are right, you have my full support to ground the type": the flack of that decision was still hitting me years later, but it was still the right thing to do. And nobody died, nor in the end was I fired for it (although a few people had a good try).
G