I initially thought that Slork was too on the nose and people were just being silly. The latter is still true for some.
But now I think that Slork is very fitting for his background.
We have a fella who's doing the job to not fade into obscurity. He keeps trying to get the name Fathom to stick, but the more successful the attempt at notoriety, the more Slork takes root and Fathom sinks.
While writing this, the thought of a washed-up yellow journalist (I believe the term originated in NY, didn't it?), who gets paid pennies, is the only one who writes about him as Fathom, and how he used to be the menace of The Deep. The journalist fears the idea of Fathom more than anything and can't stand that no one believes his stories, he is trying to save people here!
Slork, on the other hand, tries to get the journalist's articles more attention and goes out of his way to make sure the journalist *incidentally* happens upon Slork comitting horrible crimes, as often as possible; inadvertently making the journalist's writing more wild and harder to believe, even for the most credulous of nutjobs.
Obviously this idea would need more nuance to make it less cartoony. It should be funny because of how sad and drearily they both cling to relevance.