The idea of Bitcoin as electronic cash is still somewhat relevant, and there are people who use it this way. But there isn't enough adoption of Bitcoin as a form of payment, and then there's the scalability issue.
It should also be noted that even fiat is sometimes used as an investment. For example, it used to be very popular in my country to buy the USD, hodl and then sell for local fiat because our fiat suffered a lot more from inflation than the USD, so the USD was mainly seen as an investment. But it is also a type of money, there's no doubt about it. Bitcoin can easily be both, and it doesn't matter whether this is what Satoshi thought Bitcoin would become.
I understand the fact that investment is one thing everyone would want to venture once they see the opportunity and I believe that was the situation of bitcoin then. As the price began to appreciate, whales seized the opportunity to accumulate more of it withholding it in supply, making it scarce commodity while the price grows very fast.
Adoption I think is one of the major challenges facing bitcoin currently as most government frowns at it and they see it as a big threat to their fiat and other activities they do which some are quite shaddy. Although some have adopted bitcoin as a legal tender digitally and it is working very good for them. It is good that there has been a gradual individual adoption of bitcoin into various businesses which solely represents the bitcoin for goods and services goal and that would tell in time to come.