Ecosia goes beyond [just] data protection by addressing environmental concerns. Every search made through the search engine contributes to tree-planting projects worldwide, helping to combat deforestation and regenerate the planet. Ecosia planted over 215 million trees, across the planet biodiversity hotspots, making a tangible difference in the fight against climate change. Just like Mozilla, they are committed to creating a better internet, and world, for everyone.

I don't really see the big deal. And while it may be bottom of the list for you, I'm sure others might like the tree-planting thing. From what I can gather with a quick search, they actually do it properly, too, not just planting an ecologically dead monoculture of trees.

And yeah there's an "ulterior motive", although it's not really the evil scheming you're making it sound like. Ecosia paid Mozilla to include them, so now Mozilla has included them as a search option. It's one of the few ways Mozilla can get revenue, because people sure won't pay for a browser these days.