A few thoughts:
1. Is Nike sponsoring Ironman triathletes? Triathletes are huge on sponsorships, and I can’t think of a single Nike sponsored triathlete (other than former triathlete Gwen Jorgensen). Not sure why Nike doesn’t get into triathlon sponsorships, but a lot depends on where the marketing department wants to focus.
2. I’ve heard from triathletes that because men have more muscle/power, the event is usually won by who’s the strongest cyclist. You end up with these muscled-up dudes, who can’t run as fast with all the muscle.
3. For the women, they can’t put on the muscle like the men do (obviously). So they are leaner and can generally have more of a runner’s build and run comparably faster and closer to the men.