This may get a better response over at r/HistoricalWhatIf though a modernist may be able to give you some answers.

I just wanted to hop on and recommend a rather interesting read that may contain some further answers/ideas for you to follow.

Marc Bloch, one of the premier medievalists of the 20th century wrote a book entitled Strange Defeat shortly after the defeat in which he used both his experience as an officer in the French military and as a historian to analyze some of the reasons why the French were so quickly overcome by the Germans in 1940.

Take a look at it, it is a fascinating read both as a primary source and as an insight into how historical thought can be applied to non historical (i.e. contemporary) events.