I've wondered about that myself. I wanted to stay, I liked it there. But it's like many relationships in life, if both parties don't want it, it won't pan out.
Edit: I also had to take time off for studies and I suspect they really wanted all-hands-on-deck.
In their defence, they were new to having to manage people they didn't already know -- which is probably why they went back to hiring people they already knew.