Beginners Luck

Playing with the lads we have taught to play out here and got it pretty spot on till this happened. 3 players left out of 6. Marginal chip leader, dealt KK on the button, so I raised to 750 (blinds 100/200. SB fold but BB reraises to 1500. He had been playng any ace all night so reraised all in (I him covered by about 800 chips), he insta calls for the game and flips over QsJc. "What the fuck?" "I thought you were bluffing". I did try to explain that in the very small chance that I was bluffing, he still wasn't going to be a massive favourite to win, but he couldnt quite grasp it. Needless to say he flopped the staright draw which hit on the river. I went out shortly after when flopping a straight flush draw, all the chips were in but missed. Ahh well.