So if any celebrity talks about a gambling platform, this will definitely increase their traffic, as the celebrity fans will also follow him and will play at the same casino. Marketing using celebrity influence is modern day technique to gain customers and gamblers in this case.
You might have a point in your first statement but on the last one, we are talking about gambling here and not a usual product endorsed by the celebrity. Since it's about risking money thing, I doubt fans will follow that celebrity even to the point that they will consider gambling.
It also depends on the chosen celebrity as if that person is not a gambling enthusiast then become a endorser of gambling platform, the marketing might not be clicked to the viewers.