Their decline is related to hard fork events on the platform. In particular, the hard fork event of Bitcoin at the end of 2018 has caused Bitcoin and Bitcoin cash to be greatly affected, causing them to decline sharply in the long run. You see that many developers want good markets back by creating the hard fork, but the results go against their hopes.
There is no fork of Bitcoin at the end of 2018, only BCH with their hash war drama. Someone suggested that Ver and CW sold their Bitcoin to fuel the war and protect their ego which is why Bitcoin dumped too, but it is hard to determine the truth of this statement.
Now that there's little interest in ICO-s, but more interest in conducting one for your own company - competition solved a ton of issues without the need for a government to intervene and regulate.
Not sure what you're saying but essentially I get that more company want to run their own ICO? I'm pretty sure 2019 onward we won't see ICO bubbles like in 2017. Regulation will probably take place and prevent scam ICOs to run, or people will be a lot smarter in determining which ICO they wanted to participate. Most of them will probably run STO though.