It will take some time for the demand for spot ETFs to affect Bitcoin's price. Most, if not all, of the newly approved ETFs either already had their own bitcoins to offer to the first wave of investors, or they had over-the-counter deals with Coinbase (or maybe other entities) to purchase btc from them outside of normal exchange (so with no impact on the price).
At the same time, a lot of speculators start dumping, following the "buy the rumours, sell the news" tactic. Hence the price drop.