Take a look at the stats and you'll see why losing is not a surprise for Leipzig.[1
WHAT !
Why suddenly Leipzig is playing poorly, from the previous game they were good and now seen dropped dramatically, they should be able to provide fierce resistance to Schalke because they benefit from playing at home. I don't think this is luck for Schalke.
This Wednesday Leipzig will have a real exam in UEFA Champions Leage with french Lyon. So maybe players and coach analysed their positional game in attack, because Lyon will try to repeat that Schalke`s style in counterattacks.