While there are some pretty sharp folks who have read your message, none of them can read your mind, or do tests on your truck from their computer. My best guess is that you almost melted that fuse with your winching, & it was no longer up to normal demands so it failed at an unexpected time. It happens.

Fuses are just chunks of metal engineered to melt when the heat from too high a current passes through them. They are far from precise metering devices. If you had a handful of 80 amp fuses, you will likely find at least one that will let you pull 100 amps for a few seconds, & another that will blow at 70 amps in a half a second.

Don't worry about it unless you blow 2 or 3 in quick succession, then you are dealing with a serious electrical problem.

Dave