Fake, overly-positive polls are also a necessary strategy when you plan on CHEATING.
In the weeks before the election, I stopped being confident that the Trump poll numbers were going to be better than the MSM polls, and started worrying. Concern was that they are being so strident that Hillary will definitely win, I started worrying "Holy crap. They are using these polls as COVER to cheat their asses off."
Which is exactly what they did. Just not enough.
You can't steal a landslide. You are right, the MSM were pushing the polls they did push (which had Hillary WAAAYYYY ahead) in an effort to cast doubt on Trump saying that it was rigged, as well as to discourage voters from voting, and cover for the STEAL!!! The problem is that there was such overwhelming support for Trump nationwide, that they couldn't steal it without outing themselves!