Enterprises MITMing traffic is wrong, regardless of any of this; It's pretty much the reason why Google has introduced Cert Pinning, as the 'security' aspect of those boxes is utter and complete bullshit.

That's pretty silly. Enterprises are also obligated to ensure that random employees don't spirit out millions of customer account files over the Internet. If you want an unimpeded Internet connection, provide your own.

I can think of legitimate reasons for enterprises to MITM traffic. For example, protecting users against malware as a result of drive-by downloads or spear phishing campaigns. Data loss prevention is another good reason -- I would want an enterprise that I'm trusting with my credit card data to alert on payment instruments leaving their network to gmail accounts, for instance.

Employers often have legal responsibilites to their employees to ensure that those employees aren't exposed to ahem unprofessional content from other employees. The only real way to do this is to intercept and filter HTTPS traffic. Otherwise you're one HTTPS porn site away from a sexual harassment case.

Chrome will ignore the pin if there's manually installed CA on the client, exactly to allow corporate MITMing.

So, presumably they put their badly-issued "real" public cert on the checkpoint (instead of making their own captive CA and root key/cert for that), and it would have just complained/not worked, normally, but since it was mistakenly issued as CA=YES, it worked, and no one cared. Then Google discovered it because of some Chrome users behind the checkpoint.

I guess incompetence is a decent explanation here, and probably the most likely, but also provides a very convenient explanation if you wanted to hide something more sinister.

"Then Google discovered it because of some Chrome users behind the checkpoint."

And cue the banning of Chrome on government networks in 3. 2. 1...

I hope they wouldn't. It's like a canary in the coal mines. It's an easy way to be alerted to serious problems in your organisation....