This is going to sound biased since I generally despise capitalism in general but I do understand why it exist. It was made to allow for people to get ahead faster and to make more money. Capitalism is a great system for people who are motivated and want to get ahead. It also allows for people to start their own businesses and become successful. The issue lies in how companies took such a system, and loophole abuse it to submission.
The reason I hate megacorporations
1. They are motivated by profit and not the public good. This often leads to them slashing jobs, offshoring jobs, and cutting corners on safety and environmental regulations.
2. They are too big and powerful. They can bully smaller businesses, workers, and consumers.
3. They are anti-competitive. They use their size and power to monopolize markets and crush competition.
4. They are corrupt. They often use their power and influence to bribe politicians and get special favors.
and additionally, in cases of disney, sanitized anything until no rough edges remain. I dread it everytime disney has gotten a whole of another entertainment studio because it means all the good, dark, and interesting bits are going to be scrubbed away and replaced with a safe and bland product. I'm not saying disney should release edgy R-rated arthouse films, I'm just saying most of these big companies aren't interested in risk and only things which produce the top dollar.
so to answer your question, the reason a lot of people regardless of political alignment despise big companies is the result of them being a fluke that exist to affect the rest of the free market ecosystem. Monopolies are the antithesis of capitalism and should be turned down a peg.