Amazon got into the business of selling goods online, but it turns out that renting their computers to others is way more profitable

Amazon isn't stopped doing A and I would say thet they are still more known as A company - average person on street probably don't know AWS. That said, I am sure there is good examples company doing A but abondoning it to more profitable B.

F5 was a load balancer for a video game. In that article about financial concerns of pot growers in Colorado a few months back there were two people moving into services and out of growing.

And some restaurants switch to wholesaling and distributing their more noteworthy products and either close the restaurant or hand it over to somebody else to manage.

When you used to be the customer for your new product you have access to a wealth of insights about what could make the product work. If you are better at that than your old product, well...

BHP. Farming company bought by Miners. Then Mining company run by Farmers. Then steel making company run by Miners, Then Steel shipping company run by steelmakers, then corporate disaster.

Docker was originally an internal tool to power dotCloud's platform.