The bubble seems to be caused by over regulation, high cash out taxes, and lack of proof of stake or low risk interest sources. In other words an immature over regulated over taxed market is in a bubble because it's immature, over regulated and over taxed.
If the taxes weren't so high there wouldn't be so much difficulty in cashing out and there wouldn't be a bubble. But when taxes are 40% (income taxes) then you're stuck in Ethereum if you have a lot of Ethereum wealth unless you hold for 2 years straight for the capital gains rate.
Holding doesn't increase your wealth or generate any income. In fact if you just hold you lose wealth guaranteed due to Ethereum inflation which encourages people to put it into ICOs in the first place. Only proof of stake combined with tax exemption will fix this problem in my opinion.