Major decisions desks (AP, Edison, and Fox News; plus a recent newcomer called DDHQ) have made about 3 incorrect calls in their entire history (they were house races, not senate or presidential calls). An incorrect call is a HUGE deal and they have an extremely high bar for certainty. Even for Obama, who's wins were basically a landslide compared to the past 3 elections, calls weren't made until around midnight. Historically it's even common for presidential candidates to concede even before decision desks have made an official call (another norm Trump has challenged).

Anyways Decision Desks are a very different topic than pollsters and have no overlap.

I don't know what "mainstream media" you were consuming but as a bettor, I definitely didn't get the sense that the race was locked in. All major polls had Biden trailing Trump. Harris got a big boost but that only pushed her to being neck and neck with Trump. We can check the Wayback Machine to verify your claim

* NYTimes frontpage the day before the election says "turnout is a focus in a closely divided race" https://web.archive.org/web/20241105011526/https://www.nytim...

* Vox frontpage says "5 reasons Harris could win and 4 reasons Trump could" and "Should it really be this hard to beat Trump?" https://web.archive.org/web/20241106000611/https://www.vox.c...

* CNN frontpage does not include any particular characterization of chances https://web.archive.org/web/20241105000156/https://edition.c...

A cursory look at other "mainstream" media sources will easily verify that the race was clearly represented as a very close tossup.