^^^
because the tubers thought, "ohh look a wakeboard boat that makes bigger wakes... hey driver! throw me into those waves. i want to get launched!"
and the driver thought simultaneously, "I cant shake this guy on the tube... ohh look a wake boat! now i can slingshot him into that wake and knock the tuber off and i will win..."
tuber and driver in unison, "Yeeeehawww!!!"