Betting on Real Madrid is certainly not a bad decision, there are many advantages of Real Madrid compared to Dortmund which makes bettors have no doubts about betting on Real Madrid. All predictions point to Real Madrid winning, this belief arises based on Real Madrid's ability and experience in the UCL.
Betting on Real Madrid was never been a wrong decision, but it can turns become wrong decision if they all in on Real Madrid and think Real Madrid will win 100%. Whatever the teams you bet and how safe the bet is, you should only bet what you can afford to lose, the easy way is only bet with normal amount that usually you gambled on sports.
Europa League was the example, I believe there will be someone all in to bet Leverkusen since they were unbeatable.
I think that as long as they have high confidence and are prepared for any surprises that may occur, then betting any amount is not a problem. Because anyway, the problem is when they are not ready for the bad results that might happen, because if that's the case then whatever amount they bet will certainly still be a problem. But indeed, regarding Real Madrid chances in the Champions League final this season I think it is clear, that Real Madrid will remain the favorite team. It doesn't matter if we or they predict it from different perspectives, because the result will still be the same that it is difficult to say Real Madrid lost in the final this season because the opponent is Dortmund.