Crawford still had value and even in his perceived failure he still had a 700 OPS. This is also balanced by the fact that lots of baseball sees Segura as good but not great. Average defensively and his offense is less dependent on OBP - so his OPS inflates his value a bit. The consensus is that Segura is not likely to be worth $60 million over 4 years and certainly is not worth it to a rebuilding team.
Clearly the organization lost confidence in Crawford so you might as well deal him. They were always going to sell low based upon the way they talked his value to the roster down.
Now as a trade this is generally good for the Phillies. I kind of wish they had used Santana to buy a prospect, but at least they get Segura for only Crawford. And I do think Nicasio is a good, if overpaid, bounce back candidate. I like him more than Garcia for instance who probably won't last on the 40 through December. Getting an inexpensive LOOGY was necessary also. We really need 3 LHPs as part of an 8-man bullpen. I still think they go after Miller too. It is an area where clear improvement is possible.
Downside is the potential salary crunch in 4 years and maybe a lesser chance to get Machado. On balance though probably more good than bad for a team that clearly wants to compete this year. The worry is that our base of prospects is dwindling pretty quickly. We really need a healthy Sixto and then Bohm to be a real prospect.