FTFY
By default, Win96 would run that CD. You didn't tell it to. You had to go change the setting from the default. You had to tell Win95 to not autorun a CD.
More on u3: https://en.m.wikipedia.org/wiki/U3_(software)?wprov=sfti1
0: https://forums.hak5.org/topic/2843-usb-hacksaw-development/
1: https://forums.hak5.org/topic/2361-usb-switchblade-developme...
But as usual, one rotten apple spoils the entire barrel.
Having said that i did have my aunt (who is generally afraid that if she does something wrong the computer will break forever) spell me out the options in a popup (for a photo dvd she got from a photographer for a relative's graduation) over the phone once though, so i'm sure that, if nothing else, it can be a bit unexpected for less knowledgeable users.