First of all, regarding Nevada: That game was scheduled way back in 2017. It was to be played in 2020, but was postponed until this year because of COVID. The Wolfpack actually went to four straight bowl games from 2018 to 2021. Kind of hard to predict what sort of opponent PSU would have eight full years later, don't you think? Of course Nevada is not a powerhouse program, but they're not Kent State, either.
FIU was added just last year. Not sure why that is, but generally these out-of-conference games are scheduled much more than one year in advance, so most likely Penn State needed a replacement on fairly short notice.
Villanova is an FCS team, but they are a good second division program. This game was one of two with the Wildcats scheduled in 2018 (the other was played in 2021). Villanova makes the FCS playoffs about half the time, and has won 10 games in each of the last two seasons. They are located near Philadelphia, so they are a regional opponent. Lots of bigger programs do this.
Any other questions?