Good fighters can lose to lesser fighters on the night. You're not lesser than everyone that beats you. He suffered a shock defeat due to a style clash and getting his tactics wrong. He corrected that mistake, and dominated Ruiz 2nd round. I see no reason to predict a different outcome 9/10 in the future. Ruiz cannot really do anything if Joshua is leaning back with that Jab, sticking with left jabs and straight rights. Joshua will win by UD 9/10, 1/10 Ruiz wins by KO.