Technically why it's slow is entirely on CloudFlare, so I can only guess. But probably they are not mirroring files of this size across their datacenters / servers. I don't know how their public buckets hosting is done, but it's definitely very slow.
OpenFreeMap on the other hand seems almost instant for me.
In summary, on a cold start (so now when it's on HN it might be totally meaningless), the following page loads in like 8-10 sec for me: https://pmtiles.io/?url=https%3A%2F%2Fdata.source.coop%2Fpro...
Technically why it's slow is entirely on CloudFlare, so I can only guess. But probably they are not mirroring files of this size across their datacenters / servers. I don't know how their public buckets hosting is done, but it's definitely very slow.
OpenFreeMap on the other hand seems almost instant for me.