Who robs cave fish of their sight?

evolution? they don't need the eyes so they disappear?

We may never know. There was a lineup of all the likely suspects but no one could put a decent fin on any of them. I think there is something dark and fishy about the whole thing.

Random mutations and genetic drift.

In the absence of selective pressure to maintain a structure, random mutations and genetic drift will eventually reduce it to being vestigial.

We do.