Sapp has made a career of taking dives
He knows he can't compete at the top as well, so he has been making good money FOR YEARS diving
He was only serious in the beginning, but when he realized he couldn't hang with the top and STILL make good money just by being there swinging, he made a career out of it.
Watch his fight VS Ernesto Hoost in 2002 and Minotauro Nogueira in 2002.
Those were serious (but he still wasn't any good at fighting, but brute force and power)