Obviously, no 2 situations are alike; and multiple factors affect any outcome. Practically, the number of answers is infinite.
But one factor I've looked at intensively, full time for years is the role played by the brand name and/or the site's domain(s).
Think of doing business -- online or off -- as moving along a path. Some paths are rocky or go through quicksand. Others can be made straight and smooth. Obstacles can be cleared, or the surface may be lubricated.
For most niches, you'll see brand names / domains that add friction -- friction that is compensated for by extra marketing inputs ... effort or money.
Suppose your niche were nicotine patches. Well, ideally you might own NicotinePatch(es).com to simplify brand recognition, add trust, increase click-through rates, and so forth.
Traffic can be built up without an exact-match domain. No doubt about that. Still, not all domains / names perform equally well online or in the minds' of an audience.
Answers aren't always so clear cut. However, since the internet is built on domain names, domains and names are worth evaluating very deliberately.