I need help when it comes to strength.?

Im 6'1 235 pounds. i have 18 inch biceps, i bench around 250 powerclean around 180 and curl about 150 and deadlift about 380. im not big into lifting but im pretty built for my size. im at 19% body fat. im 18. just by my shoulders arms and back it literally looks like im a powerhouse that could put up 400 on a bench. but i have no idea why im so buff when im not that strong when it comes to lifting. but what i dont get is when i kickboxed and wrestled i could always overpower bigger/stronger people. like i arm wrestled my gym buddy who benches 380 and can curl 95 with one arm and i beat him. im weak when it comes to gym strength but when it comes to competitive things im really strong. this doesnt make sense. help???