See, druids are typically depicted as opposed to civilization, which on a cursory glance makes sense - you gotta wreck a lot of woodlands and shit to put up a town, and then comes domesticated livestock, agriculture, irrigation... it reshapes the world pretty heavily. And yet, at its core, a lot of the basic concepts of civilization are things that the natural world has been doing for millions of years! Gathering into communities? Same thing as any social animal does - hyenas actually form literal clans that can consist of up to 80-100 hyenas, all sharing an overlapping territory. Using tools? Birds smash stuff with rocks or skewer prey on thorns to help them rip off meat. Purposefully altering the environment to your advantage? Spiders spin webs, beavers build damns, rabbits dig burrows, and there's even bats and spiders that fold leaves to make hidey-holes for themselves. And that's not even getting into the shit that eusocial insects do...
So, the idea of a druid who decides that civilization is a part of nature too and embraces it? Not really that crazy. It's never been very mainstream, but it has caught on.
There are technically two possible interpretations of an Urban Druid. The first is basically a druid (or a shaman), but in an urban environment; somebody who looks after the health of the urban ecosystem, communing with the spirits of streets, buildings and monuments whilst tending to the animals of the city - feral cats and dogs, pigeons, crows, roaches, spiders and rats. The second is somebody who applies a druid-like mentality to the "human animals" around them, manipulating society for its own benefit. The former is the most popular interpretation, perhaps because it's more intuitive to grasp.