You have two different bags. You are to draw a ball from each of them. When you draw a ball from Bag A, it doesnt in any way affect the balls in Bag B. The probability of drawing a red ball from Bag A is independent of what you have drawn from Bag B and vice versa.
Hence, the only way you can get two red balls is when you draw a red ball from Bag A and then from bag B (order is irrelevant).