Few of the investors are putting their investment in IEO's as ICO's are already overtaken by IEO's, investors will not fade as long as they can still gain a profit in crypto currencies. They will only fade if the time will come that crypto currencies are not suitable for any profit.
I don't know much about IEOs, but I'm painfully aware of how scam ridden the ico space has become, and I say good riddance if all of them die and no new ico's come to market. There have to be better uses with which to put Eth, Neo, and other blockchains than for scam tokens. That's all the ico market has ever amounted to.
And Op, 2017 was a wild year for crypto and people were buying anything and everything they could, which of course was why it all came crashing down in 2018. Hopefully investors wised up and *if* they return to crypto they'll only choose coins with solid prospects and not overhyped scam coins and tokens.
I don't think people actually lost interest in crypto at all. They just got burned pretty badly by buying the wrong things. It takes a while before they learn to touch the hot stove again.