Up until the weekend, BTC had hit a few days of relative stability.

Everyone got bored -- wanted something to trade.

"Heyyy, these altcoins are cheap...and I can buy so many with just a few BTC"

Crazy runs on all the altcoins proceeded.

When Bitcoin volatility and growth resumed, everyone wanted back in on the cash cow. Who wants to stick with an unproven competitor when the workhorse is moving full steam ahead, right?

Once BTC settles down again, the AltCoins will have another resurgence.