I'm really interested in these coins to BTC correlations. Some btc pairs are in phase with btc other not, not all alts are the same, my guess is that some altcoins are way more traded on some exchanges that have only their btc pairs, and when BTC goes up/down, trader also buy/sell their alts. Like 50% btc 50% alts, doing the same buy/sell orders for all at the same time. Other coins can be bought/sold more easily for fiat, so traders tend to convert from btc in alts or alts in btc or just go fiat for one or another randomly, so their btc pair is sometimes in phase sometimes the opposite. BTC leads the market over the long term but in short/mid term things are more complicated.