You may be right about the Vardy "dive" but you're assuming a conscious thought process to initiate contact which, at the speed he was going, is possible but hardly certain.
At least as likely is that he was trying to move across the defender to shield the ball and get into a shooting position...
Going at the pace that these players do the only person that really knows if they dived is the player themself so I have every sympathy with the referees, though Vardy was an idiot for mouthing off.
Beats me why players do this; it never changes the decision and just gets them into more bother...