Some people who became big bitcoin investors became it as a result of holdings.
The deeper reason is the trust they give on the future of Bitcoin. Anyone won't be holding Bitcoin if they don't believe on its potential. So I think the reason why people become big bitcoin investors is because they believe that bitcoin will have a better value in the future thus holding them for a long term will give them more profit.
Investment in bitcoin can makes you developed reasoning on how to expand your income
I don't think Bitcoin investment can make us develop reasoning on how to expand our income. I believe we already acquire that reasoning before we invest in Bitcoin, and is the reason why we are investing in Bitcoin.