The post does not explain why Akamai's cert is being used. If bing over SSL were working correctly in the past---which I believe to be true---and given that Bing were using Akamai in the past, why the problem now?

Bing doesn't do SSL and never has at that domain (they previously used ssl.bing.com). you're seeing an Akamai cert because Akamai servers are hosting bing.com.

nope, bing did not work correctly in the past. A few web searches reveal that it has been like that since at least 2011.