Looked at altcoins and they've started rallying pretty hard all at once, whats the reason for this? Is it because of Bitcoin going sideways for a decent while or some other reason?
Because, altcoin prices are relatively low when compared with bitcoin, so altcoin is seen to move faster.
Along with the growing enthusiasm of citizens against cryptocurrency, bitcoin will still grow and move up albeit slowly (not as fast as altcoin), because small sales are still occurring in various exchange sites.