Crast isn't just some name. It stands for, "Careless Ruthless Autistic Sus Traveler". He was first a regal soldier, then after came what the R stands for in his name in season three. Ruthless. He joined the hunters...
Hahahahhaha, you're TOTALLY overthinking this. He's not a droid. WAIT. HE IS A DROID! LOOK AT HIM. HE'S NOT A LIVING THING!