SARS didn’t “evaporate”. The SARS coronavirus had an unusual Achilles heel, in that a person did not become infectious until after that person displayed symptoms. That enabled authorities to contact trace more effectively and quarantine etc where necessary, until it was wiped out.
Another factor that helped wipe SARS out, was that it was clearly a killer, killing a large percentage of those who got it. That quickly got everyone’s attention. You didn’t have people posting factually incorrect rubbish, or dodgy fallacious calculations saying it was no deadlier than the flu, etc.
I also understand that there didn’t seem to be any asymptotic SARS carriers, but I am not sure of this point.