Here (above) is a Derain from 1905. it's full of verve and vitality.
Here (above) is a Derain from 1909. It's OK but what a come-down! What happened? Maybe the answer is that he bought a house in the country and fatally removed himself from the influence of his friends in the city. Or maybe he acquired depressing friends out there in the country. He hung out with German friends in this period and maybe they didn't understand color the way the French did.
Here (above) is a Vlaminck from 1905. Minimal shadows, unreal color on the tree trunks, color used to contain space...it's a really wonderfull example of the fauve style.
Here (above) is a Vlaminck from the 1920's. It's OK but the painter clearly wasn't interested in experimenting anymore. What happened? Why the precipitous decline? Historians speculate that he was demoralized by his association with Picasso. Apparently Derain felt old-fashioned in the presence of Picasso's Cubist rebellion and in 1907 he destroyed his fauve paintings when he moved to a new studio. Imagine that; fauvism starts in 1905 and one of the leading practitioners feels passe' by 1907. That's how fast things were changing in those days.
Here are photo portraits of Derain (above) and Vlaminck (below). Neither had to desert fauvism. The movement still had a lot of vitality as we know from Matisse's work. Matisse stood up to Picasso and matched him, innovation for innovation. What a pity that Derain and Vlaminck chose to capitulate rather than fight.