pREORDER ISSUES- INDUSTRY SUPPLY CHAIN ISSUES, OR SOMETHING GOING ON WITH RETAILERS?

As a reader, I've noticed that popular books I'm pre-ordering are getting delayed and cancelled. It's only happening with massively popular books so far (Wind and Truth and Onyx Storm), but friends in fan communities are reporting that it's happening pretty widely. I've had two books in a row where Amazon said "Hey your book is coming later than expected", which is kind of precisely not the point of a pre-order, and definitely not something I've run into in years past. Other people's orders are being fully cancelled. Seeing it twice in rapid succession made me really curious- is there an explanation for what's going on internal to the publishing industry? Supply chain issues making it difficult to print enough books? Or is this something going on with the retailer? Not ordering enough books to satisfy demand, taking more pre-orders than it's possible to order trying to hedge against some being cancelled? I think that probably just generally it's better for me to be pre-ordering with smaller local retailers, and right now I'm thinking I'll probably pivot to that, but if the issue is that it's difficult to print enough books, it's possible that large retailers will get...I guess "first dibs" (?) and it might be even harder to get a copy elsewhere. Does anyone have any insight? I'm an industry outsider, and my brain is working overtime making up conspiracy theories! I want so badly to know what has caused this breakdown in book preorders!