While arguably it is being dumped, potentially by earlier investors from 2017 or 2016, this is overall healthy for the distribution of Bitcoins. As now, large amounts of BTC appear to be sold over OTC to large investors, those who are wanting to invest long-term, rather than short-term speculation.
This will be more sustainable for the price in the future, but it looks like there are still investors to cash in still, let's hope new investors can keep up with demand!