Huge Wordpress performance improvement with Cloudflare proxy DISABLED?

I manage a relatively large Wordpress/WooCommerce site.
In recent months the owner had noticed site performance (as reported on Google Search Console, and in GT Metrix) was progressively getting worse.

The site has server side (Varnish, etc.) and application level caching (WP Rocket).

After checking a heap of things, I took a punt and disabled Cloudflare proxy, just to see if it made any difference.

The result is simply astounding and, to be honest, a bit shocking.

This screenshot shows a representation of the GT Metrix results the site was consistently getting right up until I disabled the CF Proxy. You can also seen in the history panel the huge performance increase before and after.

also this is typical too …

This one shows what happened immediately after disabling the CF Proxy.

To be honest, I’ve never seen this site operate as fast as it is now.

This doesn’t make sense to me.

I am aware many people who report that Cloudflare is bad for performance on some of their Wordpress sites, but I’ve had anything buy minor issues (some features in CF have at times caused issues, but disabling or adjusting those features would resolve the issue).

I’d be interested to hear thoughts on why disabling CF on this site would improve its performance to such an astounding degree.