The league is more about grinding results week in and week out against the lower teams. What's the use of peaking in the league if you lose 4 and draw 3 out of your first 15 games? You're already way behind. The league and CL are two different animals altogether.
Yes, you want to be playing your best football in February to June when the ko phase starts but you can still lose. The CL is all about grabbing the big moments during the games. Look at Madrid. The only convincing CL winning campaign of theirs was 2017. The other campaigns they got outplayed most of the time. 2016 they had the easiest draws ever. A gift from UEFA.
If AM, Liverpool and Dortmund had a spine, we'd still be within touching distance of them.