Their prediction wasn't based on speed and low cost.
Every single piece I read or heard on Bitcoin talked (only) about how Visa et al skim off excessive fees and Bitcoin would be so much cheaper. I don't remember hearing anything about speed, probably because at the time nobody realized Bitcoin wouldn't be transaction latency-competitive with traditional payment solutions.
See and everything I saw was about decentralization and other blockchain/cryptography-related things. I of course saw some people talk about Bitcoin as "cheaper than bankwire", but I definitely wouldn't say that was the main driving point of all Bitcoin adopters; not even a significant minority.
Um, bitcoin was for years touted as "free and instant".