Not another conspiracy theory...
...Clube and Napier kind of over did things in their first book - "The Cosmic Serpent" - by coming up with their own revisionist history - that wouldn't have made friends. Velikovskyianism is an unforiveable sin in historical studies, especially so soon after all the arguments in the 1970s.
Things were much more receptive by 1990 when "The Cosmic Winter" came out, but what they really needed to have done is get together with historians and archeologists and "dig up" some more substantial data.