Clement Rage
Pro Adventurer
Plus, their loyalty to Shinra and each other was their defining feature, so why would they suddenly decide they didn't want to be Turks any more?
They're a lot more loyal to each other than Shinra, half of BC was the Turks dodging and being unsatisfied with their orders and superiors. They had an opportunity to leave and they took it. They're willing to come back for Tseng, but not Shinra. Makes sense to me.
Many of them joined Deepground.
And that's a piece of canon that I find completely bizarre. Deepground was top secret and completely sealed for three years, how could they know about it or get in? Why would they join an organisation Shelke describes as complete torture? Everything we know about DG indicates it's not a pleasant place to be, why is joining it a better option than leaving Midgar and taking up construction work? They were trapped in Midgar? How? Denzel could get off the plate, the Shinra building was still standing, etc.