The meaning of the sentence is that "the façade named a leader of the new Republic as the dedicator."
From Wikipedia I learn that the dedicator was a politician named Quintus Lutatius Catulus. According to the façade, Catulus gave the temple to Jupiter. That implies that the temple, in some sense, belonged to Catulus.
The context suggests that the writer does not think this is a fair assessment. Some kind of temple had been there for centuries, and it had been repeatedly worked on and rebuilt. Catulus was was there when it was finished and took the credit.
To give a modern parallel, the New York Philharmonic performs in a building in Lincoln Center that was built in 1962 and called "Philharmonic Hall." It has constantly had problems with acoustics and has been repeatedly rebuilt and remodeled, often in hope of improving the acoustics. A philanthropist named Avery Fisher made a large donation and in his honor it was renamed "Avery Fisher Hall." In 2014, in order to raise money, the orchestra removed Fisher's name and sold the naming rights to the highest bidder, and accordingly it is now called "David Geffen Hall."
The name thus reflects the name of someone rich and powerful who really had nothing to do with the building of the hall.