个人观点，供参考：

The idea of him choosing a referendum on the deal so as to break the logjam in Parliament, as this newspaper would like, is far-fetched. But then, so much about him is.

【分析】The idea…is far-fetched. But then, so much about him is.

so much about him is承接上文省略了表语far-fetched ；

也即，so much about him is. =  so much about him is far-fetched. 

【试译】像本报所希望的那样，让他（鲍里斯约翰逊）选择就脱欧协议进行全民公决来打破议会僵局，但这种想法是靠不住的。话说回来，关于他的多数言论确实是无稽之谈。

语料来源：

https://www.economist.com/leaders/2019/06/20/which-boris-would-britain-get

Which Boris would Britain get? - The Conservative leadership