put this money into the stock value itself instead of the company
It's the same thing.
manipulating the stock price
It's not because they announce it way ahead of time. Manipulation would be Apple buying a bunch of stock right before they announce the new iPhone, then selling after the announcement. That's very illegal.
Giving money to existing shareholders is completely legal (as long as you give it equally per share) because it's the shareholders' money. They own the company.
No one is being manipulated. The company is handing the stockholders their own profits. Dividends are the same thing, just taxed differently.