Think of it like a retiree trying to find a place to live where their salary isn't tied to the local economy. It opens up a lot of places with a relatively low living expenses and high quality of life.
They are immigrants, but they are immigrants with money.
My understanding is that digital nomads are basically just long-term tourists rather than immigrants; they don't get visas that allow permanent residency or anything. Iceland's digital nomad visa, for example, only lets you stick around for 6 months, and you can't renew it more than once a year. So you really do have to be somewhat nomadic, and travel to a different country.