Because the veteran Chinese pilots found ways to get into the P43s, and the nuggets, fresh from stateside training, came straight from initial fighter training in the infamous Niagara groundhog. They weren't ready for a high powered tail dragger, especially a squirrelly one like the P66.
A short coupled, exaggerated wide stance tail dragger like the P66 requires extra finesse with brakes and throttle to keep it straight on the ground. A little more throttle is needed to get it started into a turn, then when the tailwheel swivels you've suddenly got too much, and snatch the throttle back, but it keeps turning, so you stomp on opposite rudder. Unfortunately, your undersized rudder on its short fuselage moment has been deprived of slip stream, and doesn't have the authority to stop your turn, so inertia and gyroscopic precession take over and round an' round she goes. Your frantic efforts on the brake to stop this ground loop serve only to pitch her up on her nose, sudden-stopping the engine and wrenching the prop. In Jakarta, there are no spare engines or props to be had. 'Nother one bites the dust!