It might have looked like a total landslide to you, but it wasn't. He won the electoral college, she won the popular vote. The polls had it as a close election and they were off by a couple of percent.
The fact that CNN interpreted the data poorly doesn't mean the data was bad. FiveThirtyEight stated repeatedly that Clinton's lead was not insurmountable and the a typical polling error could easily flip it to Trump.
She ended up with a 1-2% preference
The same thing happens every presidential cycle. Counts come in much slower for populous states with large volumes of absentee, provisional, and mail-in ballots. Clinton is going to win these votes by something like a 2:1 margin.