Fractional ownership would enable art investors to diversify their portfolios and would reduce the entry point for investors in the space. Also, unlike planes, art is an appreciating asset.
Is there an established market for shared art ownership (besides fractional donations for tax purposes)?
If not, then I think there's a more direct and simple lesson from the failure: if there's no existing market for your idea, the most likely reason is that people don't want to buy it or use it. Thus you better have solid evidence there really exists unmet demand, probably via experiments in the earliest stages of the venture.
I don't think they had the right team for it. I did not see much creativity or innovation going on here. It's a very difficult proposition to sell someone something that they can't keep. They should have tried other methods. Maybe allowing towns to pool money together to get pricey famous art to spend a year in their museums? Or allowing anyone online to purchase a fraction of art in Iraq so that it is protected from looting - it can be toured worldwide and returned to the country when it can actually be protected. I can keep going. But they apparently chose not to.