Even though it was created in March, 2018 the lower boundary was prescient in providing support at the ~$3,150 bottom.
There's an interesting pattern here, or I could be reading too much into it.
It appears there may be a fractal pattern in the bubbles. We got 3 bubbles in 2010-11 of magnitudes 1,1,3. Then 2 bubbles in 2013 of magnitudes 2,3. Then 1 bubble of magnitude 2 in 2017.
What comes next? Triple bubbles again?
An alternative answer might be that it's just decreasing volatility. If you think so, the recent price action would like a word with you.