USFS dumped 3rd-place Mirai for 4th-place Ashley four years previously. Back then, Ashley had the cred because she'd made the GPF two years in a row. Not so in 2018. Ashley had so-so 2106-17 season and an even worse 2017 fall season. Karen had won the 2017 US Championship and was 4th at 2017 Worlds to Ashley's 7th. In 2018, Karen's cred was better than Ashley's, just as Ashley's was better than Mirai's back in 2014.
First of all, Ashley’s record leading up to 2018 was superior to Mirai’s leading up to 2014. As for Karen’s credibility leading up to 2018 being better than Ashley’s, that’s widely debatable. Karen was a mess at every one of her fall events in 2017-2018, and Ashley beat her at Skate Canada with a Bronze Medal and placed ahead of Karen in the SP at Skate America before she withdrew. Karen’s win over Ashley at 2017 Nationals was debatable, and as for Karen’s 4th place over Ashley’s 7th at Worlds - Ashley didn’t skate well, but even with 3 clean triples she was only around 5 points from Karen’s 4th place (and Karen landed twice the amount of triples that Ashley did). Between Karen showing up to the Olympics with boot problems that weren’t fully resolved and crying about not being with her mom to her mediocre placement, I think USFS made the wrong call. Ashley over Mirai in 2014 was a no-brainer, Karen over Ashley in 2018 was stupidity.