Why has Satoshi's vision for the Bitcoin as a peer-to-peer electronic cash system failed?
How did the investors ruin the vision which was similar to the Napster where data was shared at its own expense and received free of charge?
I strongly believe that Satoshi didn't personally wanted others to go for his vision of things, but he rather steeped out of the project and let others - the community to decide how they want this bitcoin to be and what path it should go for.
I don't really understand what investors have to do with bitcoin being "centralized" (I draw this centralized conclusion based on you saying Napster)? Most investors simply have paper wallets, hardware wallets etc. and they simply create value by trading and they don't influence on the bitcoin network, I mean they could through mining but so far we haven't had any problem with that, or at least I don't see this as some big issue.
Plus I don't have big issue with paying few cents with LN/SegWit at the moment. If you are looking at free transactions then check some other coins such as IOTA.