And typically a single DO droplet would suffice for a toy project or POC, for which Ansible is probably the more expedient option. But maybe they're not in a rush, and learning K8s is just another feather in their cap .
Just getting a simple deployment script in Ansible requires programming a bunch of steps - copying archive, verifying it, unpacking it, then atomically configuring the system to use the new version, finally cleaning it up - whereas with k8s you just let it know you want to Deploy something and it does.
Of course, that's only true if you already know k8s, but then again if you work with both toy and larger projects, chances are you'll have to, sooner or later.
Even if you start with k8s and you want to scale, at some point you'll want to configure your images in a predictable way with something like Ansible. Whether you do that for the images you deploy, or your configure it in situ for a single-node, it's still the same complexity cost.