Blockchain is developing, there are many new technologies, so you can not compare the situation in 2017 with the situation in 2019. Now the situation is different.
but it needs to be observed that in 2017 many victims of ico became a little allergic to the new project, because so much of the investors' money vanished by irresponsible project projects,
Yes, you are right we have seen many failed projects in both the year 2017, 2018 which they cannot deliver what they mentioned in the roadmap and this makes many people showing more interest towards IEO, even community is kept tracking about the potential projects listing in potential exchanges.
IEO became more popular because after the end of the IEO it will be listing of the exchange and investors can sell their tokens when they want.