Law enforcement at the time was even admitting (which we'd later find out to be correct) that there likely was nothing of value on the phone. It seems fairly obvious that the FBI was trying to use a high profile case to force a paradigm shift. Perhaps we can argue it'd be a good and just one, but arguing that they weren't seems not right.
Instead I am only aware from what has been published that there is the so-called "Secure Enclave" chip in the iPhone hardware manifest that will only give up its secrets to a biometric match, or a user password. That would seem to leave Apple's hands tied?
There is no world in which a post-PRISM compliant Apple cannot be coerced by the feds for an investigation. It's just a matter of how much pressure the FBI wanted to apply; Apple's colossal marketing win is the sort of thing that you would invent if you wanted to manufacture consumer trust, not "prove" anything to cryptographers. Playing devil's advocate, "authoritarian regimes" are exactly the sort of place you would send the iPhone to if you already had the information and wanted to pretend like it was hard to access.
If we assume a worst-case-scenario where Apple was already under coercion by the FBI, everything they did covers up any potential wrongdoing. It was all talk, no walk. Neither side had to show any accountability, and everyone can go on happily using their devices for private purposes.
My understanding is the suspect was detained and law enforcement was not asking for a dragnet (at least thats what they stated publicly), and they were asking for a tool for a specific phone. Apple stated the FBI was asking them to backdoor in all iPhones, then the FBI countered and said thats not what they were asking for. Apple then marched triumphantly into the moral sunset over the innocent victims'; meanwhile the FBI then send funds to a dubious group with questionable ethics and ties to authoritarian regimes.
In my opinion, Apple should have expediently helped here, if for no other reason than to prevent the funding of groups that support dragnets, but also out of moral obligation to the victims.