Leverkusen were the winners anyway. They benefited from the red card that Munich got. However, they didn't really play with an advantage over Munich who in fact were also able to create quite a lot of chances.
The result might have been different if there was no red card at the beginning of the first half. But this is football with all its surprises, Munich must accept this result and can focus more on the Champions League and Bundesliga.
Yes, the red card received by Bayern Munich is one of the factors why they lost in this match and I agree with you that maybe the result of the match would be different when they were still playing with 11 men. Statistics say they can still be superior in ball possession, that means even though they are playing with 10 men they are still very capable of making it difficult for Leverkusen. But of course losing 1 player is a very big problem, they cannot be effective in implementing strategies because of the lack of players, while they have to deal with the number of players +1.
After all, even though Bayern Munich played with only 10 players since the 17th minute, in reality Bayer Leverkusen still needed a lot of time just to score one goal. Because after all, Bayer Leverkusen also just managed to score a goal in the 69th minute and in reality, Bayern Munich still has good ability and performance even though playing with only 10 players. With statistics like that, atleast it is worthy for Bayern Munich to get a win in this match but unfortunately, Bayer Leverkusen managed to take advantage of the moment to beat Bayern Munich and also make Bayern Munich eliminated in the DFB Pokal this season.