United thumped the champions 4-1 at Old Trafford on Saturday.
Mourinho told MUTV: "It was important to win, especially after two defeats in the Premier League. It was important not to draw but to win.
"We were very strong, we felt their fragility when we scored the second goal and so we looked for more at that moment and I think we played really well.
"In the second-half, it is difficult to keep that intensity."
Mourinho continued: "(Claudio) Ranieri did very well. He knew he was losing the game, so he tried to control it. Intelligence and experience is so important in our job.
"So the second-half was about them controlling the game and us controlling the result.
"Three points and a great result for us."