Probability of winning isn't a poll - it's an opinion based on information. The information can be accurate and opinion can be waaaay off.
The actual polls, on average, weren't that far off from correct. Although I'm sure there were some poorly conducted polls that were outliers on either side.
What's good is that a simple checking of polling averages in the swingstates and nationally in 2016 along with the actual vote counts clears this up pretty quickly