We all know about the recent arrest of the person who is alleged to stole bitcoins from MtGox and laundry them through a self-created exchange.
That may be a reason why in the recent year all altcoins rise by a huge amount.
Bitcoins don't offer any privacy, as all transactions are on the public ledger. But you can put them on exchange and sell for other altcoins and then repurchase them with bitcoins. So transactions logs are not stored on blockchain only on the private exchange records. You can't do that on the exchange you don't control, as law authorities may easily track/monitor all the records. If you own the exchange, it's an entirely different story. At any point in time, you can remove all traces of all the transactions and be safe.
4 bln dollars could be enough to create a strong Altcoins FOMO. I know that this theory is a bit crazy but it's quite possible that it played a significant factor in altcoin rise.