trait.Iterator.html is 13.3 MiB in size and takes some time to load over a slow connection (not to mention render in the browser, but that’s a different issue).
It could gzip down to 0.7 MiB.
CloudFront can automatically compress files up to 10 MB in size only, and this appears to be on. https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/ServingCompressedFiles.html. According to this documentation, the fix might be somewhat involved, but it should be possible to gzip the files ahead of time and add the correct
Content-Encoding header prior to uploading to S3.
The other solution would be to ensure all files are under 10 MB.