Medium.com wrote an article covering this same topic. The results of their analysis were that quality of posts was the biggest factor in readership.
A relevant detail that I wasn’t mentioned in this article (it may have been in the medium article) was that while the days you mentioned might have been the most popular days that people posted, that is a completely arbitrary and irrelevant detail. An article that gets posted on a Saturday, if advertised on social media on a Tuesday will likely have the same readership as if it were posted on that Tuesday.
Good read though!