An example with smaller numbers: Suppose a company is worth $10 and has 10 shares. The board issues 10 more shares to one person.
Sure, the company would still be worth $10. But there are now 20 shares outstanding. Everybody except the guy who got 10 shares would see their shares fall in value from $1 to 50 cents.
Basically, issuing stock to one person has the effect, mutatis mutants, of transferring wealth from all the other shareholders to the person who got the new stock.