I don't believe the file is too large - other updates of similar size have downloaded automatically OTA - I received two updates since picking up the truck in Feb. This latest update is a safety recall and Stellantis likely wants to make sure everyone gets the update properly for legal reasons.
Navigation maps have never downloaded automatically for me, although the literature suggests that it will over wifi. I believe those are too large - currently 16.6 gigs total. The chart plotter maps for my boat do not update over wifi, although the plotter will update itself over wifi without issue. I have to download the maps to my computer, then update the plotter maps. Updates to the maps for my truck are free to download from Stellantis, and I've done a couple updates. Map updates for my Garmin portable GPS are also free, but I need to download and install those too.
That's a typo - radio updates are around 2 gigs. Similar to recent Android phone updates. The current update that is part of the recall is 2.1 gigs.