The singer quit the network after his cameo as a singing soldier was widely mocked.
But he claims he wasn't bothered by anything viewers had to say.
"I came off Twitter coz I was always intending to come off Twitter," he's now posted on Instagram.
"[It] had nothing to do with what people said about my Game of Thrones cameo.
"Why the hell would I worry what people thought about that. It's clearly awesome. Timing was just a coincidence, but believe what you want."