I would say, what you are hearing is correct - I would take all 4 of those as MAIN factors. Maybe add another two

- Verticals that you are an expert in.
- Verticals where you will have enough $$ to break into / develop / support for some time, until you start making profits.

Most startups operate at a loss for a long time, until they build critical mass of users. If you run out of money before you are profitable - what's the point?

For example, space flights are "hot" right now (space-x, blue origin, etc), but you would probably have no expertise in it, and not enough money to get into space craft biz.