Diversification is a smoothing function. You won't get as much upside holding 25-30% bonds, but your portfolio won't suffer as much on the downside. If you're young and not ready for boring old-people investments like bonds, at least limit your tech stock exposure. Go buy boring utilities or something, maybe Berkshire Hathaway B shares.
One other advantage to diversification that I hear very little about is this: if you have to sell in a down market, you can sell your bonds and hold on to your equities in the hopes they'll bounce back. Regardless, you're not held to selling depreciated assets like equities, you can sell the bonds which are boring, but probably actually went up while everything else turns to shit.
These hedge funds get wound up in complicated, leveraged, illiquid layered stacks of (often private) investment vehicles that go from highly profitable to financial nuke overnight. Thats how they just get wiped out while everyone else just has a bad day.
Ironically the whole point of “hedge” in hedge fund is for this to NOT happen but we’re seeing increasingly inexperienced players like here just building a financial nuke and then acting all surprised when it lights off.