> The whole thing was just “we don’t like that this is happening, so we’re suing.”

Typical behavior from a big company with immense resources. They probably thought they would get a settlement or SerpAPI could not afford to fight. I assume they are pretty small, at least in comparison to Google (I've never heard of them).

Google has so much money that even a "loser pays" requirement on litigation probably would not disuade them.