Campbell never really struggled at any level. Anthony had a couple spots along way where he did, if only for a short time; Salem in 2022 and 2023 were his low points covering about 65 games (he hit around .200 overall, so he had to deal with some failure).
I think Campbell was brought along too quickly. Prior to this year, he had played 137 minor league games (roughly 1 minor league season). Even now he's under 200. By contrast, Anthony played over 300. Betts played 299. Mike Trout played 291.
Mentally dealing with failure is part of baseball. I'm a huge HS wrestling fan, and I can't even count the number of multi-time state champs I've seen who you think will do well at the major collegiate level and just disappear because they can't adjust to the fact that everyone there was just as dominant in HS as they were. Campbell is struggling on the field for the first time in his life; virtually all players go through this. A bad first year means nothing (look at Mike Schmidt's rookie stats). A good first year means nothing (Joe Charboneau).