$720, $850, and $1000 are significant on the chart, and we may not have technically broken $720 until we close above it.
Most markets are driven by traders constantly cashing out and in. The same people that were in the market at $300 won't be those same participants at another price. Some people are maximising fiat, others are maximising BTC. If you're a "fiat accumulator" then you cash out at every small top and back in at the dips. So the volume is from the same traders entering and exiting again and again.Many will have joined at $300 and exited at $350