I don't recall Crawford's service time being an issue. He did not force his way into the big leagues. Of course many of us would have preferred they'd traded Galvis sooner.
Beyond that it's huge mystery. I mean, they seemed perfectly willing (even eager) to play him at 3B over Maikel but equally unwilling to prefer him at SS over Kingery. If we take things at face value, they did not rate him defensively, and did not believe he was going to bring what he showed in the minors to the big leagues. They seem to have been wrong. The injuries did not help, and to some extent it was also about the timetable and the ability to shed Santana's salary. They did not exactly dump Crawford though, he was a once-valuable player coming off a down year whom they turned into an affordable all-star while also opening up 1B for Hoskins. Just like they didn't dump Realmuto.
This is why the next two seasons are so high-stakes though. If the Phillies miss the playoffs this year and aren't a championship contender next year not having Alfaro and Crawford (and Sanchez) in 2021 while still carrying Segura, McCutchen and even possibly Herrera's salary could be a bad look.