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.
The strategy used by Dortmund when facing PSG is actually similar to the strategy used by Real Madrid during the first leg in the semi-finals. But of course Real Madrid are much better at utilizing the opportunities they get. But Dortmund can also do well. But what is really scary about Real Madrid is that Ancelotti's team is able to change strategy quickly and overwhelm their opponents. Like when Real Madrid was 1 goal behind by Bayern, we could immediately see the change in strategy in the Real Madrid squad and they immediately succeeded in equalizing the score at that time. And after that Real Madrid immediately changed their strategy back to their initial strategy. And all Real Madrid players can always resonate well in providing passes and so on. In essence, in terms of performance and teamwork, Real Madrid also looks superior to Dortmund. But it doesn't rule out the possibility that Dortmund will also be able to overwhelm Real Madrid in the final.