Real Betis is a difficult team. Chelsea have lost some matches against easy opponents before. This is now the final match and the Spanish are very well prepared for it. Also, Antony, who left Manchester United, is in incredible form. Chelsea should use their defenders well to stop him. Betis is a strong team that can beat Chelsea. Both teams have a chance to win the cup. Although Chelsea seems to have the advantage on paper, they will not be the favorites in the finals. Both teams that make it to the finals deserve the cup.
You're very correct, and I'm kind of surprised the bookies gave Chelsea 1.87 odds to win while Real Betis got 4.45 odds. I don't see much of a difference between the two teams, and I was never carried away by Chelsea's performance against Nottingham Forest during the weekend because they're inconsistent. They've lost to teams you never would have imagined this season, so the weekend performance could just be a mirage. I wish them luck but also think both teams have equal chances of winning the trophy.
It is possible that the recent trend led the bookmakers to give these odds to those teams. Chelsea has been doing much better in the last of couple of games. I still think they have a small edge in this game, but maybe not as much. However, betting on Betis Sevilla to win in regular time is quite risky. Yes the odds are worth it for some gamblers probably, but if I had to choose a winner in this game, I would go with Chelsea. Although I don't like the odds for them either as I think a draw after 90 minutes is very possible.