Most of the time when a casino is a scam and they do not want to pay they will argue that you violated their TOS in some way or form, and while you could be completely sure this was not the case they will never budge, as doing so will mean they are basically admitting they tried to scam you and now they are backtracking.
However while common sense should dictate that a casino like that will not last long, we have at least one example of a casino which has been scamming their customers for years and the casino still find ways to gain new customers somehow.
And that is a sad reality. Most people are not yet aware of these scams yet. They still fall for some sort of marketing gimmicks along with the online casino's bonuses that are often too obvious to be a scam but people still does catch those. Casino's like giving a bonus such as added hit rate when they deposit $100 dollars. Or just as mentioned b the OP, the casino's purposefully give you difficulty on withdrawing your funds until you gave up asking for it. Some closes some do not. Most reopens just with another name.
Such methods usually occur in shady casinos, small casinos or casinos that are new but cannot have enough income to cover the whole budget so decide to cheat by scamming the gamblers.
Actually, if every gambler is not easy interested with fake promotions and only plays at big and trusted casinos, of course they can avoid casino scams, but most gamblers want to find new experiences and move around casinos or be tempted by some profitable bonus promotions, so it's easy to get caught in in a scam casino.
Every gambler's expertise and experience must be honed so that they can easily determine a reputable and trusted casino.
Unfortunately, when faced with a promotional bonus, most gamblers forget about the risks that could occur.
It isn't really surprising especially if the casino is only new, hasn't made a name and reputation to uphold yet, and seems sketchy with big and enticing offers, only to find out they have a small resource fund. This is why people should be wary of the scams and schemes lurking around. If you aren't going to be careful and will be blinded by the sparkling offers, then you sure are to fall victim in this kind of fraud. And once you fall victim, the money you worked hard to have will all just be put into waste. And let's be honest here, there's only a small hope for you to recover what you've lost since these scams usually appear out of nowhere and vanishes to thin air once they got what they wanted. Hence, one must really be vigilant in distinguishing which one is worth it and which one should even be glanced upon.