Most non-professional YouTube channels start as a side project. Someone thinks of something they'd like to make videos about, starts in their spare time, and grows a following. Then the money starts to come in, and eventually it's enough for them to quit their day job and work on their YouTube channel full time. Sometimes they start a business and employ people to help along the way.

If that was a SaaS app instead of a video channel there'd be no question about whether or not it's entrepreneurial. The fact they're making videos instead of code doesn't change anything.