Understanding
Church history
How the Roman Rite came to look the way it does.
The short version: it was not designed. It accumulated, slowly, over roughly fifteen centuries, and the parts that survived did so because they were used.
The Canon is attested in substantially its present form by the sixth century. The propers of the great feasts are older than most of the churches they are sung in. Nothing in it was drafted by a committee, which is both its strength and the reason it can be difficult to explain.
Reading it properly
Liturgical history is a real discipline with real sources, and it is easy to find confident accounts online that are simply wrong in both directions. Where we can, we point to work that shows its sources on the page.