The Frank Spiekerman Mausoleum in Calvary Cemetery is unique in that the full name of the owner is written across its front, and it is the most prominent Egyptian Revival edifice in the cemetery. Bellefontaine Cemetery has the very beautiful Tate Mausoleum, also in the Egyptian Revival style.
Spiekerman donated a large number of painted miniatures to the Saint Louis Art Museum, and also was an avid dog breeder, introducing two new dog breeds to America, apparently.
His choice of the Egyptian Revival was not revealed in any newspaper articles I could find. Obviously, it has long been a source of inspiration since the ancient world.
The lotus capitals, the ankhs and scarabs are all traditional Egyptian motifs, but look closer at the center of sphere at the center of the wings below, and you see it is the Sacred Heart of Jesus.
And no Egyptian Revival mausoleum would be complete without flanking sphinxes out front.