The Australian was speaking after his successor at Spurs, Thomas Frank, was sacked this week.
Postecoglou said on the Overlap: "It's always, having been in that position twice in the last six months, it's tough, it's tough. You know that he can't be the only issue at the club and that's probably every manager.
"But, ultimately that's what we get judged on. But it goes back to me, it's a curious club Tottenham. It's made a major pivot at the end of last year, not just with me but with Daniel (Levy) leaving as well.
"You've created a whole sort of environment of uncertainty because there's no guarantees, no matter which managers you bring in because they've had world-class managers there and not had success and for what reason?
"What was the reason for such a major pivot, you know Thomas was walking in, what's his objective? What's the club's objective? At the start of the year, obviously to compete on all fronts but the club hasn't competed on all fronts for a long time.
"Also the most influential person at the club for the last 20 years is also going so if you're going to do such a major pivot, you have to understand there is going to be some instability there. Did Thomas know he was walking into that? I don't know.
"It's a fair departure from me, anyone who studies the game, it wasn't like it was a progression from me. I built that sort of squad for want of a better word to play a certain way for a number of years and he's sort of coming in and like we said, it's a curious club Tottenham."