edit: apparently it is mentioned in passing. oops.
Bananas aren't that big of a deal for most people, especially if you're looking at going from two popular varieties to one. If the Cavendish gets wiped out too, I'd say that would just be due to people not caring all that much about bananas. I can't imagine the same happening for chocolate.
If bananas went extinct (while people dependent on them were able to switch to some other food), I'd basically just shrug and get on with life. If chocolate went extinct I'd consider it a colossal disaster. I suspect I'm not alone.
But there are two points. First is that you are underestimating the kind of role a crop can play in a culture. It is not just a matter of replacing Banana with another crop. It is a matter of changing significant cultural traditions going back hundreds of years. If you think about it, the importance of chocolate is also largely cultural.
Second, it is a philosophical debate that what is more important - something that is basic nutrition for one group or something that is cultural/emotional/luxury/(I can't find the right word for the role chocolate plays) for another. Where the resources will be allocated will depend on who controls those resources and which camp they fall in.