What's the reason why some Eternatus run Draco Meteor?
there can be quite a few depending on the set, but the damage increase is noticeable.
4 SpA Eternatus Dynamax Cannon vs. 204 HP / 0 SpD Zygarde: 312-368 (76.4 - 90.1%) -- guaranteed 2HKO after Leftovers recovery
4 SpA Eternatus Draco Meteor vs. 204 HP / 0 SpD Zygarde: 408-480 (100 - 117.6%) -- guaranteed OHKO
For example, this can be crucial when trying to not get Glare'd with Eternatus in a situation where doing so loses the game. Another one that's popped up more recently is Eject Pack. Switching out when hitting a Dusk Mane is huge, letting in breakers like Choice Specs Kyogre, Dracovish, or just Magnezone to trap it freely. On offensive sets Draco Meteor just hits like a nuke.
252+ SpA Life Orb Eternatus Draco Meteor vs. 248 HP / 72 SpD Yveltal: 309-367 (67.9 - 80.6%) -- guaranteed 2HKO
Calcs like this are no joke, practically killing after any hit prior. So Draco Meteor has pretty solid uses overall, just needs to be picked right when compared to dmax cannon or dpulse.