The phrase "big promoter" refers to someone who enthusiastically supports or champions a person, idea, product, or event. They actively spread information about it to encourage others to participate or engage with it. Full definition
«If you manage to turn unhappy customers into happy ones, then they can become even bigger promoters of your business than they would have had they had a more positive experience from the beginning.» (inc.com)
He created a popular series of shows at the Gardens that bundled dinner with a package of bands, and used that to beat out bigger promoters for an exclusive contract with the venue. (canadianbusiness.com)
Francis was a big promoter of last year's peace deal with the rebel group but in visiting Colombia he will have to be sensitive to the viewpoints of the large number of conservative Roman Catholics who voted against the accord in a nationwide referendum. (premierchristianity.com)