[worst-case scenario]

Did you read the rest of the article Mr Semple wrote? He does a pretty good job on a blow-by-blow analysis.

[Slyfox]

Gas from the annulus getting past the hanger seal was the most likely source of the kick and subsequent blowout.

[allmost]

A pipe under pressure blows outwards if/when it fails. This one self crimped. You gave no response, I appreciate the referral.