The deadline is already past. It was yesterday (April 17th).
In fact, to comfortably have covered payments by yesterday, you'd have to have sold 1+ weeks ago. That lines up pretty well with that bottom in the low $6,000s. Quite a coincidence.
It could definitely be a coincidence. There are way too many variables to attribute market action to tax season. But logically, it should have some effect, given the size of the US market. It's not just one of 200 countries in the world; it's one of the largest cryptocurrency markets. I'm not sure how these estimates were arrived at, but they sound about right:
Lee said he estimated 30% of cryptocurrency holders were in the U.S., meaning $187 billion of the market value increase came from domestic traders.
We saw the same kind of action in early 2014. Maybe it's a coincidence, maybe not. You never really know with markets. Shit just happens.