I wish I could explain your “why” but I’m not sure anyone really knows conclusively. One of the greatest sticks I’ve ever fished with told me once that “there is always a fish feeding somewhere.” My experience has not always supported that but if I check the landings or reports, somebody always has caught something. I recently had one of my best walleye nights yet with no moon at all, closing in on the midnight hour. Had my partner not gotten cold, the precision trolling was locking a new fish about every 10 minutes into a new pass! (Those are the times you wish you had a second lure of the same kind!). I’ve done moonlit and moonless shore casting and produced walleyes over the same hole, same depth, same presentation. Next day, leeches on lindy rigs smoked the flats until almost 10am! Under both circumstances! But, I too have seen the opposite and wonder why.
The only thing I’ve found for consistantly shutting down a good bite is an over abundance of natural forage or a “rock-your-world” thunderstorm…. and even that.. is just my personal experience.
I tend to agree that there is always a fish biting somewhere, just some days are fewer than others and the challenge is simply find what’s able to trigger the response.
Good luck in getting this answered! I’d be very interested in some concrete evidences to help predict which conditions I’m up against before getting on the water!