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?
About what "Rally" are you speaking about?
I see only EOS was pumped for +35% and that's all. Other cryptocurrencies have a very little price movement (1-10%).
After such falls, even 10% is like a breath of air. And bitcoin is no longer so popular due to the number of appeared altcoins which are more effective and better in technology. So we wait when the altcoins will break the whole market and become a new lever of influence.