But, where are the buyers? At 6000$ the volume was ridiculously low, no one was buying, so it crashed. Now we have much better trade volumes at 4000$, but how long will it last till people who think this is cheap will stop buying and wait for price to rise or decline again. These are not the people who will push the price up. Once this money dries up, we're going back to low volumes and possible decline again. Next halving is still far away. Bitcoin needs some positive news to reverse this trend and may easily go down with some negatives.
I think 4000$ is still great for bitcoin, In Jan 2017 it was less then 1000$, when I was buying my stash it was less then 2$. Some people are still clouded by the last year's hype.
It didn't crash because volume was low. It crashed because of the bitcoin cash hard fork/hashwar/split which caused the whole market to go into fits of panic selling. Did you notice how the crash happened the day after hard fork?
At 6000s volume was low because the price stabilized and you can't trade in a market that doesn't move.
There are plenty of buyers right now, but there's also tons of panic sellers after the drop. which is why the price is moving up and down right now.