I don't know why this is surprising. Sakura Taisen was an extremely popular cross-media franchise for Sega and I imagine a significant portion of those fans didn't play the games, even though they were popular and sold well in Japan. They kept selling merch long after it mostly disappeared.
Sega president says there's been a rise in "fans who don't play the games," and their engagement with IPs can be even higher than that of gamers automaton-media.com/en/news/sega...