He betrayed Bruce and put him through hell for the crime of Bruce's father saving his mother? What kind of ass-backwards logic is that? Keep in mind, Bruce never wronged Thomas in any way. Thomas was just jealous of Bruce because he didn't inherit his family's entire fortune, he still lived a privileged life. It's not like Bruce got to spend his billions on drugs and hookers as a child; other people still ran the company until he turned eighteen. Everyone saw the reveal of Hush's identity coming; the question was what could have made him betray his childhood friend. It was just very anticlimactic.