All I say is that committing to relation of exclusivity without insurance and due diligence is risky.
The assumption no one had lawyers look at this agreement or that due diligence was not pursued is not backed up by the public facts. If you look at the original list of companies with stock impacted by the collapse, it includes very large media corporations. Given where this led, I think the more grounded conclusion is the agreement was structured and presented in such a way that it got past a lot of companies, including some with high-powered legal teams.
Stock insurance is a separate question I've not had much experience with. But I do know it may be difficult to get insurance, and it can be quite expensive. It's also quite possible, even likely, the companies had standard stock insurance, but it would not cover this situation. The stock was not destroyed or damaged. Many of the companies involved here are quite experienced, so the last is the most likely situation. They had insurance but it did not cover them here. All that said, I agree with you that insurance is important.
Thanks for noting you are in the EU. That matters for how you're viewing this. Yes, in places outside the US the sort of monopoly Diamond had for the comic book store channel might run up against serious pushback from regulators. Not in the US. The same with exclusivity clauses. The same with individual creator contracts that actively attempt to strip "moral rights" from the parties, ones that are guaranteed elsewhere in the world. Worse, state laws can further complicate dealings, and the "venue" for any legal action (which courts must be used to settle disagreements) can radically change the legal situation. Venue in deals like this would be the chosen state/county/city of the distributor, with the distributor possibly having legal residence in a state where the laws are heavily tilted in their favor. (Some states are eager to get corporate headquarters to relocate so there's a "race to the bottom" to cut regulations and oversight to attract them.)
The reality of book distribution in the US is you will likely have to sign an agreement with a distributor that gives them exclusive control of your books for certain channels. If you have enough clout, you can limit what channels are exclusive--the publisher agrees to book trade exclusivity but keeps control of Amazon sales, for example. But that's possible only if you have clout. And by clout here, I mean Hasbro/WotC level clout, and even there, the bigger distributors know anyone walking away from their deal faces limited competing options of the same caliber. The publisher also has to have either people in house who are experienced dealing with any channels they keep or a deal with a separate distributor for those channels--which may also be exclusive, for those specific channels. It probably is. And dealing directly with channels can be a massive challenge, especially since those transactions are tilted against the publisher, too, particularly when dealing with Amazon and other corporate behemoths, who increasingly control the major distribution channels.
That doesn't make these good agreements. That's the reality of the current market for distribution in the US. I always support companies and individuals pushing back against these deals when possible. I'm just describing the current reality of the market.
If you can't accept the constraining, often exclusive deals from the limited number of operations set up to, say, handle your book channel distribution, you are free not to sign. You can always sign with the smaller distribution operations, if they exist. (For a decade or more, even the "indie" distribution options have been vanishing; Publishers Group West was gobbled up by Ingram in 2016, for example.) Or you can hope the bookstores will order direct from you. Which is very unlikely to happen, as bookstores are far more likely to stock what they can get easily from their usual general distribution sources. Stores have limited bandwidth to chase down individual books from individual publishers and pay for shipping for one or two copies of something. The best stores will do that, but it comes with a cost to them. And I note that with sympathy, as I have done a fair bit of work with a local comics, games, and pop culture retailer for a number of years.
I could go on about how absolutely broken the distribution system is for books, comics, and games. Publishers are at a huge disadvantage in these transactions, and the legal field in US-centered transactions is pretty much always tilted in favor of the mega-corps and wannabe mega-corps.
