I guess excellent service and transparency builds reputation. It is true thay it takes time and patience to build reputation. A random accusation cannot destroy a reputable casino. Loyal platform users will eventually defend a casino if they know based on their experience that they are truthful of their service. But it is true with just one wrong move, year long reputation can be damaged or be gone in a short span of time.
That's true every highly reputable gambling casino has its community of loyal followers and they will defend its reputation against fake reviews and if there are legit complaints they will urge the admin to resolve the issue because they too do not want to play in a gambling site with existing complaints, I will also defend a gambling site I'm playing if there are fake reviews.
The fake reviews will not have a chance to trick or slander the casino because the casino will try to defend and proves that they are not guilty. Even they will try to investigate it to find which people want to get them down.
The reputations can go away with one mistake and everything that they build from a long time ago can ruin. That is why the casino will not trying to make a mistake and they see a problem, and they will help their customer to solve the problem.