The distinction, I note, on how a coach is discussed revolves around two items, whom is doing the assessing, and what that assessor knows about coaching. Any person whom lands a job as a college coach at any level, without yet having worked a day, can coach. But that fact may not have any bearing on them being successful.
Yes, one can be a good coach and not find success. Some of that can be circumstance with other staff, support, etc, and some can be a misfit in style or scheme.
An excellent coach can flourish in less favorable conditions, but only if they are a match to those worked with in style and scheme. A good coach needs more help. How this applies in the arguments posted here is that few of us are capable of determining the variable involved, and without having been a coach themselves, can really only speak to one observable item.
Was the coach successful here or not. That we can all see. As to why, that can only accurately be known by those in the profession, and even then, likely not fully without talking to someone involved.
From my vantage, Austin was not successful in garnering the type of performance needed from these kids. As to how good a coach he is, I don't know anywhere in the neighborhood of enough to assess that. I would only hope that someone arguing his level of ability would have themselves coached that position at the level to which they ascribe him.
And while it matters not to me what someone calls another (nor calls me for that matter), I have read multiple accounts of Austin's players expressing their fondness and appreciation for him. It would be extremely difficult for me to term such a person as "trash".