They weren’t. Aggregated polling in 2016 gave Trump a 1/3 chance of winning. That’s not low. It’s actually quite likely. Him becoming president was invariably within the margin of error in many polls.

Eg. 2016

https://projects.fivethirtyeight.com/2016-election-forecast/

2020:

https://projects.fivethirtyeight.com/2020-election-forecast/

https://projects.fivethirtyeight.com/2020-election-forecast/senate/

https://projects.fivethirtyeight.com/2020-election-forecast/house/

2022:

https://projects.fivethirtyeight.com/2022-election-forecast/

The media reporting on polls (and anything scientific for that matter) is universally abysmal, that’s why you mistakenly think otherwise.