Prime video uses a non-AWS CDN when I watch football on it here in the UK

The BBC were unable to find a single CDN that could serve the UK during its peak football matches. https://www.bbc.co.uk/webarchive/https%3A%2F%2Fwww.bbc.co.uk...

that's called load balancing and regional availability. many companies do multi-cdn. in fact it's smart to use multiple CDNs so you can do better in contract time. Twitch uses IVS but we have failover to other CDNs for very large events.

I'd believe it - CloudFront always felt a bit like AWS ticking a box ("we have a CDN") rather than being a good to use product.