It's obvious the difference in quality but we never know where the surprise will be, will Chelsea lose? That would be normal in my opinion.

The Premier league decider made Chelsea more determined to win and now they're doing that job again this final so I think Chelsea will win this one.
I wouldn't even be surprised if Chelsea lost dramatically.
Lol everyone has the right to make predictions but that doesn't mean your prediction is right or wrong, even the person so confident might be getting it wrong so they are just mere predictions that might not happen.
There is difference in squad strength and it's obvious that Chelsea are stronger than Betis but that doesn't rule out the possibility of Betis beating Chelsea. This is a final and all teams will definitely come prepared. Chelsea have had the mindset of qualifying for the Champions league or Europa league even when they didn't have hope in making top 4 they were determined to win the Conference league and get a spot in the Europa league at least but to their surprise they made top 4 and now in the champions league now they will want to win the title to have a more successful season.
Chelsea could lose as you mentioned but I would be surprised if they do.
Haha that's how it is, no one knows our guesses, but everyone has their own choices.

Chelsea is now much different from last season and Maresca has at least brought changes by being able to improve the quality of the game to qualify for the Champions League and can get the conference league trophy.
Just one step away --- maybe the preparation has been done from before and they must be mentally prepared lest when in the final they appear less dominant.