Fedora contributors are the ones maintaining the packages and they might have more work now if something breaks on the M1. This only "helps" Red Hat in that they can get more testing on ARM.
"But the main reason is that there have been many issues surrounding the maintenance of ARM packages for Arch Linux, and that the Fedora team is both capable and willing to provide provide the support needed to provide a truly polished Linux experience on modern Macs (the main goal of the Asahi Linux project). By moving to Fedora, the Asahi team can focus on reverse engineering Apple hardware while the Fedora team can focus on maintaining the distribution itself on the Apple Silicon platform. This combination of Fedora with the Asahi boot components and drivers for Apple Silicon is called Fedora Asahi Remix."
This is a bidirectional relationship, the Asahi linux developers also benefit from the people and infrastructure in Fedora.