du carnaval versus du carnaval

Justin, 

this is a possessive construction, using the structure in French of ‘ (possession) de (owner) ‘. 

In English  ‘ carnival’s tradition ‘, with the possessive apostrophe used. 

As per attached links to the lesson here and to Laura Lawless site, in French, as well as the word order change required, when the owner is not represented by a proper noun ( carnaval ), it must be preceded by a modifier, hence ‘ du carnaval ‘ is the obligatory contraction of ‘ de le carnaval ‘ 

 Expressing possession in French with "de"

https://www.lawlessfrench.com/grammar/possessive-de/