Will they? Only if they can. Tech industries are example #1 for this behavior. At some point very few people can create a competitor for Amazon, Google, or Apple.

Apple has lots of competitors and doesn't even have dominant market share.

Google is hard to compete with due to network effects, because they don't often miss tricks, and because they've invested so heavily in core R&D for so many years. The classical story about competition is that a big rich company becomes complacent and stops improving their products, opening a gap for new companies to enter, but Google hasn't really done that, they continue to tweak and try new things (arguments about search quality specifically for precise programmer queries aside).

Amazon retail is hard to compete with because it's not a very good business. They keep margins extremely low for not entirely rational reasons, which is why most of their profit now comes from AWS. AWS meanwhile does have competitors.

That would be true if not for regulatory burdens that larger companies can afford to shoulder. We just watched a progression from "OpenAI has no moat" to OpenAI begging Congress for regulations to stop them from killing grandma. If you can't get a foothold in the market there's no point in acquiring you.

What are some examples of this occurring?