Its hot. Fish die. It happens. Could have been anglers, could have been anything.
There are scientific reports that say good fish handling is far more superior to water temps. I know of one musky I killed with a deep hook, and there was nothing I could do about it. It was a small fish, deep hooked right in the gills. What can you do? Have all my other muskies released fine? As far as I know, yes, but who really knows?? I see a lot more people fishing muskies these days, so there has to be more rookies, and instagram stars more concerned with social media likes than the fishes well being. Mine don't leave the net. Unless its a big one, I rarely even take a pic. My musky net doesn't leave the boat, and I don't fish bass at all.