It will only be on luck, if Dortmund should win this Champions league. When it comes to performance from the start of the season Dortmund are no where near Madrid, even Dortmund is aware and would need to step up their game, if their performance would be as that of how they faced PSG then their is no chances of winning Madrid during the semi final against PSG they played tactically moderate and with that approach they can't win in the finals even Madrid plays a lot more defensive. Still very unimaginable how good Madrid is at converting even the slightest opportunity, Dortmund should play very defensive and make good use of opportunity if they really want to win the game.
If Dortmund can really beat Real Madrid in the Champions League final, I think it will be lucky because if I look closely, Dortmund doesn't have a very strong attack like Real Madrid, even when they beat PSG in the semifinals, in my opinion, it's not as good as Real Madrid when they beat Bayern Munich, which is really great dramatic. Luck or surprise factors can happen in football but we know how Real Madrid performed in the Champions League, he has good experience and Carlo Anceloti has a lot of smart tactics to defeat his opponents so with all Carlo Anceloti's hard work I think his club still has a bigger chance of winning. won the Champions League final.
Real Madrid this season was extraordinary, they were able to beat great clubs who were strong candidates in the Champions League, while Dortmund only eliminated underdog clubs from the round of 16 until reaching the final, so Dortmund was quite lucky this season. Even though in the end they failed to win the Champions League title, they still won so far it is quite appreciated that it is not easy to reach the final when most people do not really favor Dortmund in the Champions League, this season will be a season of pride for German clubs because the two big clubs have represented the semifinals and reached the final.(Bayern and Dortmund).