Alex Smith had his best statistical season in 2017. I’m sure Reid took a conservative approach, to try and get his elusive ring. It would have been pretty ballsy to throw a rookie in there, but I’m sure despite the blow back Reid would’ve initially received, Pat would’ve adjusted just fine.
Plus, some coaches make dumb decisions. Much like Del Harris not making Kobe Bryant a full time starter until almost year 3. It took injuries to 2 guys for Kobe to get a good consecutive starting gig. It’s not that he didn’t have the talent and gifts, his coach was just a stubborn.
Just bc guys are head coaches, doesn’t mean they are perfect or they make the correct call every single time.