You’d want to look at the market fundamentals carefully: if that company has high fixed costs and lacks strong customer lock-in, problems with satisfying customer needs, etc., you might reasonably think you could pick up customers with better pricing or support.
A great example is Uber: they’re dominant but they have a ton of debt and neither their customers nor, especially drivers, have a reason to stick with them if the money is better somewhere else. They could conceivably make that up through superior logistics but if you thought you could do better, say in a particular geographic area where you can get drivers who know where anything is, it might be reasonable to compete if the absence of such a huge amount of debt gives you enough leeway to support an app development team and treat your drivers enough better that they’ll favor your clients.
