Galar and Kalos are close. Megas are crystalized souls of dead Pokemon juicing up the Pokemon with Infinity Energy, and its been told to be painful. So. What I figure is that since Gigantamax looks to not require an item, then what fuels them? Infinity Energy. And what do we know about gyms and raid spots? That they are in specific spots that can bring about D-Max/G-Max. Sooooo, think about them like Ley Lines, where the gyms line up to allow Pokemon to tap into infinity energy. Also, think about the angry red energy and clouds forming around the Pokemon. All that pent up energy in megas now is releasing much more easily thanks to the giant size of the Pokemom, making this True Mega Evolution.
More so, the ley lines will look like the alchemic diagram for the elements, it lines up. And further more, we will be able to catch Xerneas and Yveltal in the post game, as they will likely be revealed to be from Galar. That crater in the wall and the forest south of the Starting Town? Yeah those are its natural habitats.
Its finally time for Deepest Lore to finally happen, and there is no stopping the hype train!