Leverkusen is playing with one man down, and that will definitely affect their performance. I am shocked that Leverkusen cannot score any goal, but rather they're playing with frustration on the field. This match has really proved that Bayern is stronger than Leverkusen this season in all competitions. Winning a team like Leverkusen on a clean sheet is miraculous.
The defeat suffered by Leverkusen will be difficult to reverse in the second leg even though the second leg will be held at Leverkusen's home ground. I even agree with what you said that wherever Munich is much stronger than Leverkusen this season in all competitions so Leverkusen's domestic defeat to Munich is also very normal. But losing badly in the Champions League is something that is very painful for Leverkusen even though there is still a chance in the second leg.