A casino site does not gain trust through running a review campaign, as a matter of fact, some dubious casinos with dubious intent can still run a review campaign at the beginning of their journey to gain users and their trust, but I tell you that it's only a foolish person who will give their trust to the casino simply because they ran a review campaign.
Why not?
It is possible as it is part of their business, so if they keep their promise, pay to review campaign participants fairly by themselves or by review campaign manager (outsource), it's helpful for their reputation.
It's one of ways of gaining reputation but there are more important contributors for their reputation: platform operations: deposit, withdraw, provably fairness and more.
And it's like you read but didn't understand what I said, haven't you seen casinos that ran multiple review campaigns and even signature ad campaigns only for purpose of building trust and reputation, and as soon as they've gained this, they absconded with users deposits?
I am not or did not say that casinos don't gain trust through review campaigns and all that, but I am saying that we as users should look beyond fully trusting a casino simply because of they ran a review campaign and were able to pay their users, their overall short or midterm performance in their service to their customers is what tells if a casino should indeed be fully trusted or not.