That's exactly it, they were happy to take some money and then simply sign off on what he said without doing their job and checking it properly and let other parties use their (Mazars') valuations to make - no doubt big and important - financial decisions, but now that he is being investigated and it may well turn out that what he said was nonsense they are disavowing it. But that's not much use to all the people during the last ten years who have loaned money to Trump based on their valuations. I seriously doubt Mazars are going to return their fee for all that work even though they have just admitted that what they did was essentially worth nothing - and even less are they gonna recompense anyone who lost money by making decisions based on their worthless work.
There is a whole industry of companies and people who audit, review, credit-score and so on other companies - and it's an important job of course cos you need an independent valuation of something to decide whether to lend them money, sell to them on credit, go into business with them etc etc - and yet how often do we read about companies providing a clean bill of health to someone or something that goes hugely bankrupt? For me it feels as though it's one of the biggest scandals in the financial world - that the people and companies who are paid to check on the state of a company and whose reviews are relied on by countless other parties get away without punishment when their assessments turn out to be completely wrong.
As far as I have been able to tell, the ratings agencies that failed so badly in 2008 - they just waved everything through, which worked fine until it didn't - got away completely unscathed with no punishment and, seemingly, no damage to their reputation or credibility.
Non-executive director is pretty much the only job I have ever heard of where there is a sort of tacit understanding that no-one will actually do it properly. They are normally paid to attend one meeting every quarter or so and as a rule they get an awful lot of money for very little work. In theory the non-execs are supposed keep some kind of watch on the executives and prevent them from fucking up but I can't think of a single time when non-execs have somehow managed to restrain the people they were supposed to be watching and save a company. In fact what normally happens is it's pretty obvious that the job is viewed is money for nothing and when a company goes bust they are surprised to discover there was something they were supposed to have been doing.
At least when it emerged that Arthur Anderson's auditing of Enron was worthless then AA actually went down with Enron though Anderson Consulting had just split off from the parent company and was able to survive. That's one of the rare cases that I can think of when the guys who assured everyone that the totally fucked company didn't manage to get away with their criminal incompetence. The fact that they went out of business felt like a fair punishment and satisfying in that way... but as it just reduced the "big five" auditing firms to a "big four" meaning even fewer companies that could possibly audit huge companies, with less competition and no doubt ever cosier relationships between checker and checkee, I can't help thinking it did nothing to deal with the problem as a whole.
But anyway, that's besides the main point, which is that Trump's own accountants are saying that his own valuations of his properties are unsafe... which means that he almost certainly lied about them, either to secure loans for more than they were worth, or to illegally decrease his tax liability - or, and let's face it, cos we're talking Trump it's the most likely, for both. Both pretty serious crimes I'd have thought.