Maybe the ideas or innovations of a project have already ceased to exist, that's why ICO is currently almost 100% non-existent. that is in my opinion manipulating the previous project idea so that today we usually call it a scammer. I think the ICO trend can return to its peak, if we can take the trust of an investor again. very sad to see the graph that was made by the OP, even though investing in the ICO project was very profitable in its time.
Very sad that it would far from reality to gather back investors interest, with how those many scam projects push them away the chance is too little.
We can't blame those who lose a lots of investment during the peak time of those scam projects, millions of dollars are being runaway. Developers needs to bring up something that will be unique and interesting in order to have new investors to join inside this types of industry.
Let's accept the fact that ICO is now dead, its sad reality as this an easy way for legit project to raised fund, but this was easy way for scammers to collect fund at their own interest too, so it is better that ICO will be gone forever, and IEO is now rising , so it is more legit and can be trusted, we just need to choose the right team, platform, mission, vision so we will know if feasible or not.