Earlier quoted context omitted.
You're not answering the question I'm asking. I'm not looking for a treatise. I'm just asking how investors keeping vacant supply off the market could make money in the face of increasing supply. They have to pay to hold the houses. They're not earning income from the houses (they're vacant). Supply of the houses is increasing. Fill in the "???" before "profit".
If investors keep houses off the market that artificially reduces supply. All they need is for the increased prices to outweigh any price decline that comes from increased supply. This can happen with or without vacancies for example by having pricing power in the rental market. House vacancies aren’t my central argument however - they are a symptom of the wealth distribution problem causing our housing crisis.
It's fine if you just don't have an answer. But then my point is: nobody seems to have an answer about how this is supposed to work.