There's a Chromium bug that goes into more details, but the basic idea was that they didn't want the cert details button to be in the Page Info pop up, but didn't have a new place to put it. In Chrome 56, the SSL icon now shows "Secure" or "Not Secure", so more users will be clicking on Page Info, and they didn't like technical details in that pane. There's a new bug to find a better place for certificate details in Chrome 57.

https://bugs.chromium.org/p/chromium/issues/detail?id=646465

https://bugs.chromium.org/p/chromium/issues/detail?id=663971