Auba and Mkh were signed to replace Gotze's position in the team as they changed tactics, they also made the CL Final so they had a lot of money and used it. Which is well exactly the case of the team we're talking about right now.
Also I will repeat again. The Mkh of Tuchel and the last year of Klopp are totally different. In the first time around the league he took 30+ shots and only put 7 on target. He scored 5 goals for Klopp. For Tuchel he scored 23 goals, then he moved teams twice and flopped both times and never did that again. So how much of that are we to attribute to good luck and bad luck? He scored more than 5 at United and Arsenal despite being terrible. Also when they were at the bottom of the table they were 4th in xG, so again, how much does luck factor into something like this?
Also FWIW under Tuchel they didn't have to take the Europa League group very seriously which obviously helped with potential fatigue.