With respectable auditors, independence is what you're paying for. Auditors that are found out not to be independent quickly go up in smoke. Just ask anybody who worked at Arthur Andersen about the Enron scandal.
Arthur Anderson was founded in 1913, so they were around for quite some time before they "went up in smoke". Anderson started auditing in the early 90s, and apparently was ignoring serious red flags from the very beginning. I guess auditors can get away with biased/dependent behavior for a long time.
Yes, but they lasted for a nearly a century first. While corrupt auditors will fail _eventually_, it isn't realistic to expect auditors to all be honest because they bad behavior will kill them in the long run. They can do a lot of damage in the short term before they fall apart.
It'll be interesting to see how this situation shakes out for this auditor, but I suspect they'll keep ticking along just fine.