Bayern Munich is not much of a favorite right now because of some of the disappointing results they have had in previous matches. Lazio's aggregate is not big and maybe Bayern Munich can make a comeback in the second leg because the match will take place at Bayern Munich's home ground. Now it depends on Tuchel and how they can get a win in the second leg, as people say that Tuchel is not the right coach to handle Bayern Munich now.
They will not lose Bundesliga to Leverkusen but if they have to choose between Bundesliga and Champions League, they will choose Champions League. If they beat Lazio and go to quarter finals, they will not be too far from the final match. They will possibly keep fighting in both competitions as in Champions League, with knock out format, it will be risky to be eliminated. In Bundesliga, it is a long run so Bayern Munich will not give up soon.
I don't see any hope for Bayern Munich for taking over the table from Leverkusen, they have 8 points interval and with the current form of Leverkusen now Bayern Munich have to exercise patience this season and allow Xabi Alonso to finish what he has started, as for the Champions league Lazio are already taking lead and Lazio will see it as an advantage to qualify to quarter finals, the both teams seem to have equal performance but still Lazio have to put more effort despite they have won the first leg, the second leg will be a little bit difficult to win because despite Bayern Munich performance are fluctuating they don't joke with home game which I fill the can make it to quarter final.
The only way for Bayern Munich to get pass Leverkusen in the league standing right now is for Leverkusen to lose 3 matches and for Bayern Munich to win all their remaining matches in the league but judging from the performance of the league leaders Leverkusen, despite gapping Bayern Munich with 8 points they always appear to be more serious in every match they play and they have never allowed their recent good performance to get into their head as have have been doing better and better in every match which is the reason why I think they will be the champions this season. For the Champions League match involving Bayern and Lazio which will be played in Germany, I think Bayern Munich still have more chances of getting to the next round since it will be taking place in their home with the support of their fans they have a better advantage than Lazio.