If the decider doesnt have many data points, they're going to find points to support their hunch. This person works out super hard, the did a marathon, super good at chess, being hot will open some doors, anything goes.
The reality is most of the deals are made through friendly intros, and vet you for a certain lingo and overall fitness to be fundable.
Good luck correcting this culture. Are you going to evaluate the deals you missed, and go "eh to be fair the guy was a slob and came from a no name school, and we under estimated grit / timing"?. It's not like the data that shows youre bad at data driven evaluation is going to sway someone who isn't data minded.