1: Is fishing luck or skill?
I feel that 80% of catching fish has to do with the skill of the fisherman and presentation of the bait. Do you have the best bait where it belongs to catch fish? Have you presented the bait correctly to excite a bite? How much skill did you use in placing the bait in the correct place in the water strata. That includes both depth and distance from fish attractants such as weeds, brush and underwater contour.
I also feel the 20% has to do with luck. If you go fishing on a lake you know then fishing is a matter of timing. If you are in the right place at the right time you can just be there for a bite by accident. This is where the luck is involved. I can't even tell you the amount of times I've come back into the dock to people who haven't caught fish and I had caught my share of fish on that day.
A: You can learn from an experienced fisherman and from books.
B: You can spend a lot of time on the water to increase your odds.
C: you can experiment with different baits and presentations to increase your odds.
2: Why do some fisherman always catch more fish?
I would think you can also answer this question with the 80/20 rule. The 80/20 rule works a little differently here. The reason it's different is 80% of the fish are caught by 20% of the fishermen. That leaves 20% of the fish to be caught by the other 80% of the fishermen. The 20% of the fishermen who are the skilled fishermen and have learned what the fish want to entice them to bite are the ones who catch fish.
There have been days when I knew from my fish finder that the fish where out deep and beyond the cast of the shore fishermen. There were other times that I could see a pocket in the weeds and if I drifted the bait into the pocket I would get a bite. I had an advantage of knowledge and boat position.