Irrationality is a matter of perspective. Cryptos are still a relatively small market from a global economic perspective. From a technical standpoint it's in a bubble, but all the new investment money creates a sort of unknown factor.  A lot of altcoins are being actively developed with unique tech so it makes sense that the wealth from bitcoin and ETH would trickle down and affect the altcoins.  Combined with the problems getting miners to agree to progress, and it's just simple healthy competition and speculation. That's all I'm going to say about it.