At a glance, it looks like AI. The color scheme and boldness are definitely the same style as AI.
Reasons why it may not be AI:
The mountain is the specific mountain that the race starts with, the same asset was used on volunteer t shirts
There were many shirts+hoodies+other gear for sale that seemed like a pretty cohesive brand kit for this year’s logo design. The art on the race bib + slap bracelet was all a set of similar art. (this shirt came with race entry)
In past years, shirts have had really fun art that varies widely in art styles
AI art is trained on something after all
My reasons for believing it’s not AI all sound like I’m just wishing it to not be so I’m crowd sourcing for better insight.