I'd start from a slightly more-charitable assumption which ends up in a slightly different "Hold up that's a little optimistic" territory.

1. Yes, if someone generally invested in "dot-com stocks" before that crash--covering both winners and losers--they might today have a surprising amount of (potential) dollars.

2. However much of that impressive-looking sum would be just because of 25-30 years in the market.

3. So we need to scale that "very rich" against someone putting the same money into an total-stock market index fund back then, which may not make it look nearly as impressive.

I could have been more charitable. I think their key word was "big" tech. The blue chips. What were the tech blue chips before the dotcom crash? Microsoft, Cisco, Intel, IBM, Oracle, Etc. Some might call Enron blue chip. I think their point mostly holds though. If you'd have invested in the blue chips and held you'd likely do well.