I think it was a combination of forces. Price was moving in a tight range. Bulls failed on their last try up in October, so it was the bears' turn to try and force a breakout.

Heading into the crash, shorts were low and longs were high, implying weak bid support and lots of fuel for selling. Some large sellers, perhaps including Craig Wright and his rich friends, capitalized on the BCH FUD and low liquidity order books, causing a selloff. During other times this year, buyers were bullish enough to step in and absorb this kind of selling pressure. This time around, the books were empty. The market was finally ready to crash.

I think it's healthy for the long term, yes. People were too hopeful and bullish. This kind of reset is all part of the general market cycle. The same thing happened in 2014. I would guess price will bottom out anytime between early December and late March. Then we'll probably see a show of strength from bulls and some sideways for several months as the market confirms the bottom is in.