I stand to be corrected, Lumen, but globally are not the majority of Protestants "mainstream Protestant" without any inclination towards the prosperity gospel; and even among fundamentalist Protestants, surely the majority does not ascribe to the prosperity gospel?

Although the prosperity gospel is preached in huge US churches with a heavy TV presence, surely "a huge TV presence" does not equate with "a huge number of Protestants"? 

As for increasing influence, as the Trump phenomenon and the European populist movements show, many will listen is you tell them what they want to hear.