GAC, 2.5 mil difference against opponent

There is always a reason why someone with a bigger roster than yours is at the same skill rating. I just won against a guy with 1M more GP than me, 6 GL to my 4, Exec r9 to my Exec r8. Why? He had a poor def, he failed on my Geos and Nego, and he had terrible mods. There’s always a reason.