Amazon: people like books; people like next day delivery of stuff; people and companies like making stuff and running stuff in Amazon web services
Minecraft: Marcus Persson owned the game studio (and wrote quite a bit of the game) that made Minecraft, lots of people like it, Microsoft was willing to buy it for billions
Kiran Mazumdan-Shaw made beer, people like beer. They then used beer making processes to make biotech medicines - people like being alive and will pay a lot to stay alive, or even just a bit healthier
His parents were not all that well off. They invested $300,000 in his new company. That’s within the ability of many middle class workers
His parents were employees, not business owners.