There is no level of diversification or foresight that can protect the masses from major bubble collapses.
Sure there is. It's so easy, you probably can't see it. Just stay away from individual companies, even individual industries, invest broadly across the market as a whole and ignore collapses - just ride them out. If you invest in some SP500 or "all stocks" fund, or whatever, you've own the same micro-% of the American economy before, during, and after the crash, and through the recovery. The exchange rate between USD and "micro-% of all sticks" may fluctuate wildly for a while, but just don't sell in a panic and you'll be fine in a few years.
The closer you get to retirement, to more you'll need some share of your investments in quality bonds, so that if you need money to live on through a crash bottom you won't need to sell stock. (Government bonds are not quality bonds any more - after the US government punished ratings agencies who dared question the rating of US debt, you can never again trust any sovereign debt rating in the US - just steer clear of the category.) The old-school rule of thumb was "your age as a % in bonds", but that's from a time when interest rates were quite high. Less than half your age as a % in bonds is probably a mistake, however - you need something to be selling that's not stocks when everyone is screaming about the end of the financial world in every decade's crash.
Don't over-think the problem, don't act out of emotion, just accumulate wealth and have patience. In times when everyone seems emotional about the market, make damn sure you're not being emotional before you take any action. I've sailed through the dot-com crash, the 08 finance crash, and I'm fully expected the next one will be along soon enough, but you just keep accumulating "micro-% of all stocks" regardless and, sure enough, you become more wealthy over time.