I suspect it depends on the customer/target audience.

If you target developers, open source vs closed source will make a difference. For others, customers probably don't even know what GitHub is.

This is not necessarily true. Wrong monetization can be the killing blow. Market can change and your business model which used to work can suddenly fall apart. A recent example for business model change is Tailwind where traffic to their open-source docs plummeted and suddenly not enough people are upgrading to their commercial licenses.

Startups die for a variety of reasons, even if products are popular and loved.