That's not true.
Diversification is a wealth preservation technique, not a wealth creation technique.
It is likely that if you are starting out without having a lot of resources, then it is better to NOT diversify, even though surely it can take a long time to build wealth to such an extent that it starts to make sense to diversify... and people will arrive at those decisions about how much and when to diversify at different times, but surely diversification is meant to protect your investment rather than growing your investment - even though it is possible that you could have some portions of your investment that are more directed at growth, and then other areas of your investment that are more likely to conserve value.
I really love your clear expression about what he said..
Like I often sees people always saying diversification is means of wealth creation sometimes I came to the sense that how would it automatically create wealth for such person alternatively I looked at it on the other angle that if someone invested in a very trusted and reliable business and it runs for about 1 years to 20 years also considering the age of the investor it then automatically turns out to be a wealth creation depending on the shares of which him or she maybe they are holding in that firm or industry. If such business happens to make huge profits and increased dynamically due to how such firm and business is being managed then we can say it's sure to be a wealth create, typically example are Amazon, Apple, Samsung and Google, Microsoft.
I believe those who supported their dreams and make investment earlier owned a share, they would sure know and understand such investment is truly a wealth creation considering the net worth of these companies today and their Global dominance. Anyone who own a shares however have it in their mind they must need to diversify their investments rather to choose the right investment to invest. Taking from your words, I can really be sure as preservations of investment instead of diversification.
Then from the post title, investment somethings guaranteed their success it depends on what form of investment they have chosen because investing in a non profitable company may either sink their investment and kills their dreams on how they had structured their investment and their life cycling, life cycling I mean is about their age variation and differences if they are within the age of 55 and make investment and expected to yield within the 10 years to 20 years time just as Microsoft took years to get to this points may sometimes makes the investors not to venture into such investment because they would believed that they are out of age cycling.
Which is the reason why it's always advisable for we as a young people to venture into the right investment to secure our future, and to me I have seen Bitcoin to have that exact assurance of securing one's future and its good to hold bitcoin for long time as I strongly believe it has come to stay just as other well known firms today but somehow and overly, mentally and analytically it would stay as long as we are still alive just as fiat are being used today so will bitcoin remain in existence.
Hence diversification of wealth isn't a guaranteed way of making one rich rather to chose and locate the right investment that is the only way to make one rich.