could you not hire a few data scientists to answer more questions, ,in stack overflow, this rate is much much higher..
Neither StackOverflow.com nor CrossValidated.com hires anyone to answer the questions. Both sites rely solely on volunteers. You could ask StackExchange.com why they do not pay people for answering questions, but the likely answer would be that this would be a bad business model (how would they profit from it?).
Moreover, I'm afraid that the kind of people that you would like to answer questions for money would likely not be the same group of people you would like to answer them. If you are an expert in your field, then you can easily find a more interesting, and better paid, job than question answering on some Q&A site. On the other hand, the existence of sites like this shows that you can attract people like this to help others, but obviously, none of them would be doing this full time.
We could make many guesses why the response rate on StackOverflow.com is higher (is it?), e.g. it has more users, or it focuses on questions with reproducible examples, i.e. well-defined problems. On CrossValidated.com many of the questions are open-ended, often ambiguous, etc., but there is not much we can do about it.