Regarding the gaps that need to be filled – I see it this way:

On the way up, only a few people bought in the 70-80 range, while a lot more bought in the 60s and 90s. So when the price drops back into the 70s-80s, there aren't many traders with a strong "attachment" to these levels.

For example, if your average buy price was 60 and you’re scared of further declines, you won’t be too concerned whether you sell at 85 or 79—you’re still in profit. In that situation, you’d likely hit the sell button at market price just to exit quickly.

However, when the price reaches levels where a lot of people previously bought (indicating high volume), a significant amount of selling pressure is required to push through. Since many of those buyers have already sold on the way down, the remaining ones are likely unwilling to sell at the same price they bought a few months ago.