It is not a luck, the luck won't last in the whole season. It is the result of high commitment in building Leverkusen to be a stronger and established team. Leverkusen can perform consistently in all competitions (Bundelisga, Europa league, DFB Pokal). If it is just about luck, Bayer Leverkusen won't be unbeaten in all the competitions.
I agree with you. Luck will not give you an unbeaten record like Leverkusen. To be honest, I saw several teams who won the league title by luck. There are several teams that have had the misfortune of failing to win the title and providing good luck to other teams. You can see Dortmund in the 2022/2023 season. They failed to win the Bundesliga title after drawing in the last match. Munich and Dortmund both collected 71 points but "unfortunately" Dortmund lost due to goal difference.
What happened to Leverkusen was not luck. It was the dedication, commitment and hard work of the entire team that made them an unbeatable team this season.