The Newcastle manager pulled out of talks with Celtic which led to Postecoglou taking the job.
He told BBC Sport: "I've got to thank Eddie Howe because that was pretty much done. At the end, Eddie, for a number of reasons, just didn't feel comfortable taking the role. They'd gone so far down the path of him being appointed that it was really late.
"Pre-season was about to start and they had to make a quick decision. After that, I think they just saw something in me, with nothing to lose. I was looking forward to it because it was the bit that was missing. I'd had the success but I hadn't had it in a place where I knew it could be impactful.
"I wanted to be in that environment. was a moment. Me and my wife just sat there saying 'It's happening.' At the age of 55, it was happening."