Board Thread:Warhammer 40k General Discussion/@comment-71.91.63.134-20150907060405/@comment-86.176.31.119-20151206202554

Guilliman tries to consolidate what he can to keep what he has access to safe for the future, be that with or without the Emperor and the rest of the Imperium.

It takes him most of the book to actually convince himself and even then he tries to open the command of the second Imperium to Lion or others.

When cut off from command lines it's good judgement to create the strongest alternative command you can until more information is known.

The only reason it was ever really thought to be a 'bad' idea is that some might not understand the need for strong leadership in the situation presented (which the Primarchs had little information of) and that it would be seen as a simple power grab rather than consolidation. Also it shows pragmatism rather than faith which again could be mis-judged.