There are four scenarios to consider:
First is that the company is a awful place to work, and people give up and bail out quickly. One hint of this is "fast moving environment which rapidly changing priorities". If you see something like this for work that normally requires thought and takes time to do, it's dysfunctional. You won't do any better there than the string of ex-s they already have.
Second is that the organization can't describe what they want and can't evaluate a candidate in any meaningful way. I saw a job posting running for ten years that was obviously for a programmer, but beyond that I couldn't figure out what they wanted. I now have that job, because what they needed in part was someone that could 'read user's minds'. Not that I can, but I have the strategy to learn what they need.
Third, if the job has 20 'Requirements', and each is reasonably specific, they may be eliminating every candidate in the country. They can't find anyone because they're expecting some kind of 'super-employee' that, if they exist at all, are making a lot of money working for a very appreciative employer.
Forth - location, pay, environment. I saw an ad for an instrumentation programmer in Edmonton Canada working in an 'oil upgrading' refinery that belonged to the Sovereign Wealth Fund of Dubai. Normally such people would be found on the US Gulf Coast, working for a US major oil company. A US candidate would first have to situate themselves in Canada, second figure out whether working for a Middle Eastern employer is better or worse than an American one, and third figure out whether they can handle the role. This is a big risk given the distances and uncertainties involved.