but the main community is holding the funds, the marketing, the names, ect.

No they are not. Block.one is. Block.one has no obligation to use those assets to the benefit of 'the main community'. A year is a long time. If you don't think that the developer team may fragment and have diverging views how to launch the platform, change its view on the best way to launch the platform in a year, diverge with at least some significant component of the community, or finally that other important marketplace changes may occur over the course of a year then you haven't been around much.

I'm not claiming that the ICO is a bad investment. It may be a good investment. But it presents a significant risks that do not apply to many other ICOs where there is no such split between the tokens investors are buying and the tokens actually used by the platform. This is not just 'anything can happen'. It complicates things greatly. In practice, it may make no difference, but that can't be assured, and you are being unrealistic to dismiss the issue and especially to do so with simplistic single cases such as 'Average Joe and his cousin' which do not at all represent the universe of reasonably plausible outcomes.

For the last example, it is unlikely, also it would require those investors to form a consensus among themselves rather than dispute one another, thus causing their movement to fizzle to nothing.

This is complete nonsense and exactly the kind of maximalist "there can be only one" rhetoric that has disproven again and again. Divergent views and diverse platforms do not lead directly to a movement fizzling to nothing. You are too dismissive of the possibility of many varied outcomes, some good for ICO investors, some not, but the latter is not at all equivalent to 'the movement fizzling to nothing'. It is very possible that ICO investors could be left in the dust and EOS or some variant thereof could still spawn a very successful movement.

Furthermore, they are going to have to convince non-investors to run their Genesis block... and why would anyone do that when no one has heard of them?

One last time, you presume that no one has heard of them. They could in fact be extremely well-known investors, or could have sufficient resources to make themselves well-known, and as for why anyone would support their chain: 1) perhaps their idea of a distribution is more favorable to newcomers, who didn't participate in the ICO, 2) just look at the 1000s of chains that already exist, dozens of which are reasonably successful (and a significant fraction, including of the successful ones, are fork chains). It seems getting participants to support a chain is readily achievable in practice.