Sandro still wasn't kicked out. Lucifer was. But that wasn't done by a single superhero, but by a whole huge army. Heroes are an integral part of the M&M plot. And the 8th part is very important for the universe; after all, it's a turning point in the war of the Ancients against the Krigans.

Exactly! Sandro just lay low until better times came. By the way, when I played the 4th one before, I came across three amateur Campaigns about Sandro's revenge. Just as an aside—they don't rewrite the world history, but you can feel the popular love.
And in Axoth, there are even fewer monsters from the Krigans. Moreover, how could they run away from their native element? I wonder what remained in place of the old world? Scorched earth, hot lava, or did the Krigans proliferate—does anyone know?