It was "dumped" in pre-Christmas week during a notoriously crowded month, which meant Sony either
A) wanted to hit that Avatar/Hobbit sci-fi audience,
OR
B ) they didn't know how to sell an action cartoon on a franchise whose live-action movies were suffering bad critical comparisons to Disney's MCU, sneaked it out the traditional week of the year that the critics were on vacation, and, like WB's Aquaman, hoped they'd get a few core fanboys in between the rest of the traffic jam.
Certainly the fact that it WAS non-MCU Sony-Spidey (and the "Miles, not Peter" looked like cheap petty studio rivalry) made non-fanboy audiences wary during its first release, until the "No way?...Way!" word of mouth from those who did see it started to kick in by after-Christmas school-vacation and the January empty-theater doldrums.