Because the volume is increasing and that millions cannot affect on the market anymore if there's someone think about manipulating the market and use that amount.

We don't know what's going to happen here and let see if that situation you have mentioned like a single company is dominating could give bad effect on Bitcoin in future. But hopefully they won't do any nasty thing and think about killing the market especially if they think about taking the profit. For now let's enjoy those thing they do since we can't deny that those accumulations they did add more demand for Bitcoin.