Beethoven's Piano Sonata #32 features syncopation quite prominently. Where did this influence come from musically, and why did it not become more widespread after he utilized it? It seems like a one time anomaly until it reappeared in African American music decades (if not a century) later.

I can't answer, but I thought it might be useful to add some context: I presume OP is thinking particularly of the second movement, and the syncopated rhythms in the first three variations. Each variation doubles the speed of the notes, but continues with the syncopations.

Here they are with the score (NB: I am not affiliated to this YouTube channel in any way) --

1st variation (12m 48s)
2nd variation (15m 15s)
3rd variation (16m 47s)

Since OP mentions parallels in African American music, I'd suggest a particular point of comparison to highlight is a walking bass moment near the start of the 2nd variation.