The "crash" wasn't a day-long, week-long, or even month-long stock pricing event, but lasted 6+ months from the first tech sector to the last going through the crash.<p>The first stocks to get hit were the web 1.0 properties in Q1'00 (use Amazon (ticker: AMZN) or Yahoo (YHOO) as a proxy as there aren't many left standing that are easy to find historical prices for) and amongst the last were the comm equipment companies which didn't peak until 6-9 months later (e.g., Cisco (CSCO) or Ciena(CIEN)).<p>All of this is completely separate from whether any of these companies had viable business models. Some did, like the telecoms, their suppliers, semiconductors, enterprise software. Some did not, like pets.com.<p>A very small number of dot-coms survived, and ultimately thrived after the crash (AMZN). Though you would have had to have enormous foresight to properly select your investments during the boom to not lose a ton of money if you bought in this frothy period.<p>All of the company fundamentals were well known at the time. It's not like the enormous cash burns of certain types of businesses was hidden from view. It was a badge of honor at the time (also true today in a few places). Some of that cash made it into other businesses that had been around for almost 100 years, like HP or Lucent, but juiced them, and they suffered withdrawal symptoms when their customers stopped spending (or even paying their bills).<p>To a fundamental investor, the perplexing thing about the whole era was looking at one of many not particularly unique companies that was trading at 25x annual sales, growing 50% a year, and losing money (which is a ludicrous valuation for a public company). Yet you'd find it at 40x three months later.<p>To get back to your question, having been close to the situation, I can't point to a specific event that started the cascade, but once it started, there was no stopping it. To a fundamental investor in early 2000, the outcome was perceived as being inevitable, but impossible to predict when it would happen. If you'd asked them at the time, they would have told you that the tech market had detached from fundamental behavior back in 1997/98 earlier with no signs of slowing down.<p>As an aside, if you were willing to look outside tech, it was an amazing buying opportunity in pretty much every other sector of the stock market. Industrials, energy, commodities, real estate, and so on were trading at discount prices even in the midst of this enormous bull market in tech/telecom and related stocks. Unfortunately that is not the case today and it's hard to find any sector that could be considered cheap.