The most bizarre thing is that this is a known issue that folks have asked them for ways to mitigate, to no avail. The reddit thread even links to an extremely weird dialogue where Netlify's response boils down to, "if you're hosting a small site that gets DDoS'd, don't." https://answers.netlify.com/t/limit-bandwidth-to-avoid-high-...
I've dealt with Netlify's support [1], and one of their CS heads was incredibly rude to me and blamed me for the problem they created.