What is mentality of CPS? A man I know raised 4 boy /w his wife (now divorced) & all 4 boys have been in jail?

2 are on probation for felonies, 1 is so messed up on drugs that he gets SSI since he can not even think right to work & one is serving 30 years for attempted murder of a public official. The man married the best friend of his wife & she left her child w/ the father b/c it interfered with the bars. He works, makes a good living but has not changed. NOW CPS has removed his grandchildren from the foster home they were in and is letting him adopt these children, Since he still goes to bars, was such a failure the first time around, what makes CPS think he will do better this time around? I don't understand their way of thinking. He even taught his boys the way to "neuter" a dog was to tie a rubber band around the "privates" until they just feel off plus he got the boys up each morning with "up you little MF" - this was from his own mouth, not second hand information. What chance do these little kids have in this family?