When WP articles are properly edited, the contributors are not supposed to engage in original research. Also, they are supposed to CITE THEIR SOURCES.
If you go to the bottom of any given WP page the primary and secondary sources are supposed to be there. But this is not always the case because, as I previously noted, the majority of WP editors are amateurs. And as well meaning as they may be they are not trained to properly vet sources and write neutral, yet also analytical, commentary.