I do not know what the team proposed to the managers, but they need to realize that if they want to advertise here, they need to allocate certain funds for the marketing which includes the manager's fee and the participant's payments. No one will be willing to work on the condition that if we can bring you sales, the gambling team will pay us and if there is no sales, there may be no payment. Also, such a model is not transparent because the site can always show fake stats in order to avoid or lower the payments.
They need to think that so many trusted gambling sites are advertising through signature campaigns for long time, meaning that the ROI to advertisement on this forum is good one.
OP did not know or did any research on how a signature campaign works here in Bitcointalk, what he is proposing is for the manager to spend their funds and they will do a profit-sharing, they don't need a signature manager all they need people who will promote their project on their own.
Checking their business model, it is profitable for affiliate marketers but no bounty manager will accept this kind of scheme, if OP is the main developer of the project then I agree that he spends his own funds and gets 100% of the profit, so why not try a month campaign and see the results, you can repeat if the campaign is successful.