I haven't realized until recently many polls are slanted to influence the outcome of the election. If Biden is ahead in the CNN poll why I would a vote for Trump if he isn't going to win ? And lets face it, most of media doesn't want Trump to remain in office so their polls are going to show Biden with an insurmountable lead.
Polls are incredibly easy to fake, just select the right people to poll and you will get the outcome that you prefer.
There are internal polls and public polls. Internal polls are expensive and paid for by the candidate. These poll results aren't released to the public. These internal polls are used to plan campaign time and generate ad buys. On September 15, for example, Biden campaigned in Florida presumably because his internal polling showed he was slipping in Florida. The public will not find out what the campaigns knows because it's not in their best interest.
Biden is running a "rope a dope" campaign. That's a boxing term where one fighter protects his face and backs into the ropes to avoid taking punches and to tire out his opponent. Biden's campaign is giving him limited exposure since he can't take a punch. And the Biden campaign is hoping Trump will self destruct. They may be right.