Byu beat #1 Gonzaga last year and they went to the national title game. Any team can lose to a top 100 program.
The programs aren't really comparable. Unm didn't even make the dance the year we beat them and they haven't been past the round of 32 since the 70's.
You are comparing beating an NIT team to beating a top 10 team who was in the national championship last year.
The program for unm in 2001 is nothing like Gonzaga in 2018.