"No African American Senators were Democrats until 1993" is sort of misleading in that it implies that there were Republican African-American Senators at that time, but that's not true. There was one black GOP Senator from Massachusetts who served from 1967 to 1979. Before that you have to go all the way back to Reconstruction.
https://en.wikipedia.org/wiki/List_of_African-American_United_States_senators
"ThE dEmOcRaT pArTy HaS cHaNgEd"
Well, yeah. The Democratic Party has changed a lot since 1993 and certainly since Reconstruction. As has the Republican Party, under Trump, radically.
Any way you slice it, there haven't been a lot of black U.S. Senators in our history, which is shameful, but lately most African-Americans to become Senators have been Democrats.