Mike, to me, the answer your question requires study of the history of the development of golf course architecture in the US and also our economic history.
Macdonald builds NGLA in 1911, borrows features from the best courses overseas, and he blows away everything that is on the ground in the US. (Not just the holes, but his advances in turf quality.) That sparks a huge demand for golf courses of similar quality. This happens to coincide with 20 years of great economic growth, so there is funding for this demand.
Many people want Macdonald to build their course but he is not interested in traveling all over the US so he only designs a handful of courses. He tells them to hire Raynor, and Seth is happy to traverse the country to do this work. I imagine that wealthy men in cities all across the country are contacting Raynor (and Tilly, Emmet and Ross and others) because they know their current courses are not up to the new standard.
Everything Raynor knows about gca he learned from CBM, so he reproduces the templates, giving the owners exactly what they wanted. Raynor does not fit the holes as beautifully in the land as CBM, but the templates are such good holes to start with that all the Raynor courses are good and the features are clearly distinctive. So the Raynor style, while slightly different than CBM, creates it own demand. Raynor's business grows so he hires Banks (and Barton) to help. When Raynor dies in 1926, Banks finishes ongoing projects like Fishers Island and gets a few jobs on his own. The first is my home course, Hackensack, which Banks starts in the summer of 1926. We received "propositions" (they did not call them proposals) from Banks, Stiles & Van Kleek, and Tillinghast, with Ross declining because he was too busy. (Had Hackensack hired Tilly, this week's Northern Trust would not be at Ridgewood... Tilly would not have been hired the next year to build another course 5 miles away!)
There is still enough demand for the Macdonald-Raynor style for a few years, but then the Great Depression hits. Banks' business naturally falls off (he never comes back to build the third nine at Hackensack) and then there is relatively little new golf course construction for the next 25 years. Golf is simply not that popular. Baseball, boxing and horse racing dominate the sports scene and that does not change until Palmer (and then Nicklaus) come along. When significant course construction finally starts again in the late 50's, there is no one alive on the Macdonald/Raynor/Banks tree. RTJ and Wilson build in their style, and THAT style, which fits the new equipment, begins to dominate. (Hackensack hires William Gordon in 1960 to change our Banks course into a Dick Wilson/RTJ course... Damn our Modernization Committee!)
So there's my long-winded answer to your question!