When they were an expansion team...my giants fandom faded over the next couple years into nothing.
I was also never a BYU fan growing up...casually followed ASU...remember cheering for ASU vs BYU my freshman year(The Harden game) but by my sophomore year I was a BYU fan.
Think a lot has to do with how casual my previous fandoms were. Suns and Cardinals(now Dbacks too) we’re always my diehard fandoms...can’t imagine switching allegiances from them. Especially Suns, zero chance of that.