Different diameter and pitch. M33×1.00 for Mavic, vs. 1.290" (32.76mm) and 1.320" (33.53mm) × 24TPI (1.06mm) for ISO and Campag respectively. They're close enough, and thread tolerances are wide enough, that you can gronk Campag and maybe even ISO onto a Mavic hub, but it will damage the hub threads.
Different diameter and pitch. M33×1.00 for Mavic, vs. 1.290" (32.76mm) and 1.320" (33.53mm) × 24TPI (1.06mm) for ISO and Campag respectively. They're close enough, and thread tolerances are wide enough, that you can gronk Campag and maybe even ISO onto a Mavic hub, but it will damage the hub threads.