Thanks for your help troubleshooting, Monika!
When I turned off the font preview, Illustrator did not crash while searching for fonts; when I turned it back on and searched again, it immediately crashed.
I have 500+ fonts.
When I ran the validate fonts feature in Font Book, it found 30-some fonts with issues or were duplicates. I removed these, but it didn't seem to prevent Illustrator from crashing.
Can you say more about font management? Is that something that's a part of the Mac OS system, like Font Book, or an additional app installed? I don't recall ever installing anything additional for managing fonts.