> You can’t diversify radically from your own company and at the same time tell investors it’s the future and it’s going to be trillion dollar business etc.

Sure you can; in fact in many cases you should. Say, one knows (to keep things scientific; replace "knows" with "honestly believes" to somewhat reflect real life) his $100M invested in a company to have a 50% chance of being worth $1B in 5 years and 50% chance of being worthless.

This means expected 500% return in 5 years, which should make (diversified) investors pour money in. But as a real person with $100M net worth, I do not want a 50% chance of zero net worth at any expected return rate. I would rather get $80-90M today, which will give my family 100% chance of financial independence, and leave $10-20M in as a riskier bet. My 2c.