Viv ...by mentioning those names you are still assuming that what they say is credible, it may well be but the ancient world and understanding of forces which have a bearing on our existence are far more than the sum of those you mention , I presume that you will agree?
The fact that spirit was identified as no more than the air we breathe is very plausible given human reasoning and understanding and the complexities of same, as is the fact that some saw it as a supernatural force, hence the very foundation of why we discuss it today and certainly a causal factor for your question.
In the context of spirit as merely the air we breathe who could argue with certainty that ancient peole saw it as just that.
The main reasoning and acceptance of spirit as something other than a physical force comes to us courtesy of the bible and such like.
The proportionality of those writers as opposed to wordwide population is miniscule.
What comes down to us in the evolution of language and ultimately the vocabulary we use is not down to those writers of mystical stories, but rather normal generational handing down.
I therefore see no confusion the ancient understanding of spirit being no more than the air we breathe as a physical force based on the evidence of effects of such is entirely possible,
The fact that it came to be seen as something other than that ie magic or supernatural was most probably down to a tiny minority in relation to world population, the effects of which have persisted to this day ie the minority speaking for and influencing the many.