Bayer Leverkusen only defeat of last season was in the UEFA Europa League final against Atalanta and there's no way a team would be so lucky to almost finish an entire season unbeaten. Xabi Alonso found the best tactical approach that brought out the best from his team players and that was what made them stand out. Wether they manage to repeat such impressiveness this new season or not, it doesn't change the fact that hard-work, tactical masterpiece and ability helped them achieve everything they did achieve last season.
I totally agree you about Bayer Leverkusen great season. They only lost one game which was final against Atalanta. That shows how well they played all season. Their coach Xabi Alonso is very smart and figured out how to make his team play their best. He got most out of his players. We do not know if they can do it again this season but last season they worked hard made smart decisions and played well. Alonso is great coach because he can make plan and make it work. Bayer Leverkusen success shows what can happen when you have talented players work hard and make smart decisions.