Likely because Cloudflare flagged it, there was a risk for Cloudflare to take all Bubble apps down because of this one copyright infringement that Cloudflare found.
Also, I’m pretty sure that Cloudflare only goes after copyright infringement when someone reports it to them. So likely what happened was someone found your app violating copyright laws, and looked up your domain name and who hosts it, it said Cloudflare, so Cloudflare told Bubble and Bubble probably took action because they didn’t want their Cloudflare account to be closed/suspended and bring down all of Bubble for everyone which would have been a bigger headache to clean up.