Facebook didn't start as a startup, neither did Google, neither did Craigslist.

True, but for those looking to start a company there is very little to glean from these examples as they are massive outliers. These are some of the most successful web companies/products in history their story does not reflect the average of successful companies.

There are over 5,000 more companies earning >1M/yr and even far more earning <1M/yr. There you will find more useful information to learn from.