Good question, Tom. I presume Thompson's "flamboyant" style was in his genes... unleashed with the help of a bottle perhaps!
Not many architects in the mid 1920s, besides Dr. MacKenzie, were doing the type of bunker work Thompson did at Jasper (1925) and Banff (1927), and a few years later, St. George's. Therefore, what could he have seen that would have been an influence on him in this regard? I don't know, but I can't think of anything.
Forget the bunkers though. I've always thought there's overemphasis on the brilliance Thompson's typical bunker style. More Thompson holes are "wild" and adventerous because of his outstanding use of native ground, than the aesthetic value of the bunkers -- 15 through 18 at Capilano come immediately to mind; as do 9, 13, 14 and 15 at Jasper; and the Cauldron Hole at Banff, of course. 2, 4, 5, 7, 8, 14 and 15 at St. George's too; and, 1, 2, 4, 7, 8, 13, 15, 16 and 18 at Highlands Links!
All of the aforementioned holes would be eternally exciting to play if every bunker were filled in tomorrow.
Getting back to your original question, I have to say Thompson was a pioneer.