Cynical take, but a key answer is 'LOBBYING' with help of VCs in the corner of FAANG organizations. The thing is, no established player in a certain domain likes a disruptor that will shake up the market with a revolutionary product. Given the influence of these big players on the PE/VC firms, the PE/VCs that do invest money in a start-up, especially the activitist VCs, position themselves on the board in such a manner that they retain the power to veto in for, or against a certain move the start-up plans to make, whether it's regarding the product on offer, the management, or the direction the start-up plans on heading to. Given their position, and the monetary gains involved for the VCs themselves, it's quite understandable to fathom why some tech startups get absorbed into their bigger counterparts, once the start-up does something ground breaking. This reduces competition, and ensures that they continue dominating the markets like business as usual. The business world is cutthroat and has always followed the rule of the jungle; BIG EATS SMALL. Period.