There is a detailed examination of his case at this link
http://www.washingtonhistoryonline.org/leschi/
Ive not read all of it myself but would expect the answer to your question to be there.
Unfortunately the "quashing" of his sentence came far too late to save him from being hung
There are several reasons why monotheism was unusual in its time and place, but the main reason is that the major cultures such as Greece had been polytheistic.
The battle of 1812 was the war of 1812
