The point is you don't build wealth by diversification, what's the need of having so many asset and so little invested in all, as a bitcoin investor you should focus on building a good stash in bitcoin first before you think of diversifying, then when you have at least a while year of your living expenses in bitcoin then you can consider diversifying into other asset.
I don't know how you arrived at this statement but I have noticed it to be the case with most of the world's billionaires, they became rich through a single product before some of them diversified. Bill Gate, Jeff Bezos, Elon Musk and many others were all known for a single product which made them rich before they later diversified into others things. So it could be said that starting an investment career or wealth creation process might require one to focus on one asset which in our case is Bitcoin, this way it will be given the attention it deserves. Diversification should only be consider probably when one have riched his portfolio objectives in terms Bitcoin stash.
Bitcoin right now has more potential than any other asset I know, so it's a better idea to focus on building my Portfolio in it and this could take up to 4 years before I can have a whole year of my living expenses in bitcoin because of how much I'm investing now and it could also differ with someone else.
Most times diversification is not just about the profit margin but as a way of spreading the risk. People diversify on the basis of hedging against risk so that they will remain afloat ni matter what the future throws at them.