It is not established that it is a scam. Most of the people in the cryptocurrency ecosystem are scammers, yes. Even popular figures like Dan Held, Tuur Demester, Meltem Demirors, Tone Vays and others are merely pyramid scheme facilitators in that they try desperately to get you to buy into it so that their own holdings increase in value. However, the tech itself is interesting and is not a scam. Well, at least it used to be interesting. Right now studying bitcoin is like studying horse carriages - it can be an interesting hobby and maybe a career in some parts of the world, but most people drive cars these days and knowing how to operate and fix those is way smarter. Ethereum is the car to Bitcoin’s horse carriage.