1. Netflix is a 300B company, this isn't a resources issue.
2. This isn't the first time they have done live streaming at this scale either. They already have prior failure experience, you expect the 2nd time to be better, if not perfect.
3. There were plenty of time between first massive live streaming to second. Meaning plenty of time to learn and iterate.
Peak traffic is very expensive to run, because you're building capacity that will be empty/unsused when the event ends. Who'd pay for that? That's why it's tricky and that's why Akamai charges these insane prices for live streaming.
A "public" secret in that network layer is usually not redundant in your datacenter even if it's promised. To have redundant network you'd need to double your investment and it'll seat idle of at 50% max capacity. For 2hr downtime per year when you restart the high-capacity routers it's not cost efficient for most clients.
There is no middle ground where you commit a mediocre amount of resources, end up with downtime and a mediocre experience, and then go “but we saved money.”
They indeed have a great CDN network, but it's not very good for this particular type of traffic. May be they will know/fix/buy next time...
But like you stated, they dont want to spend money and their technical people couldn't deliver on time. This isn't a technical issue a lot of people on HN and Twitter wants to discuss about. It is a management issue.