Bobby glared at John before he dropped off the boys. He couldn’t stand the man, never did. He wasn’t a good father; never letting Sam and Dean some semblance of a childhood. He had enough of John Winchester and his obsession.
The bruise on Dean face is how Bobby came to his decision. All it took was a few connects and call to CPS; the boys would be staying with him and John Winchester would never be able to come within a mile of his house.
He might have to give up a life of hunting but he would do anything for his boys.