Existing payment networks already are fast, cheap and I'll also throw in secure. (In Europe ATMs and bank-to-bank transfers are free.) They could easily be made simple to use given the requisite will.

You're correct about payment in the developed world.

But the Libra website highlight potential usage in developing countries. I may be wrong but in my opinion there is a huge market to take over in the countries where one has a Facebook account before having a bank account.

I can't find the link but I came across an article explaining that in Myanmar Facebook and "internet" are basically synonyms. That's because when most of the population began to have access to the internet it was only via Facebook services that are provided freely thanks to a commercial agreement between mobile providers and Facebook.

Now just imagine if Libra could pull something like that for payment services in all developing countries.

Fast, secure, but not cheap. Credit card merchant fees are on the order of 2% + 0.15 cents per transaction. The industry would still be profitable with prices orders of magnitude lower. A combination of regulatory capture and high fixed infrastructure costs have protected those profits -- but with cell phones, the infrastructure barrier need no longer apply.

Indeed, the average civilian will probably not even associate Zuckbucks with "Bitcoin"...