They never knew that the purpose of creating Bitcoin was to gain transparency against traditional currencies which still depend on central banks and financial institutions based on several explanations behind the main purpose of creating Bitcoin by Satoshi Nakamoto.

In the Bitcoin white paper, the introductory section that I read is still relevant to the current situation that trading on the internet still depends on third party financial systems. The presence of decentralized Bitcoin provides a very transparent system so that anyone can know every transaction that occurs.
Maybe those who think Bitcoin is a scam have never read the Bitcoin white paper so they are never willing to find out how the Bitcoin system works.

It's really not knowledge-based that people think Bitcoin is a scam.