As I said in another comment: The up-front payment is the only thing that makes sense for Cloudflare. You got a customer that's costing you money each month. They broke ToS. You offer them a deal still to keep the services running. And their CEO/CFO tells you they are looking at other providers like Fastly.
If Cloudflare gave them a monthly contract then the casino would simply pay for a month and switch over their services to a competitor in that time. So Cloudflare loses all the money from the past (where the casino used far too much traffic) and will barely recoup 10k (minus the running cost, so more likely 7k at the high end) for a single month. It's just not worth it.
So they offer: Stick with us for a full year at least or get fucked. Which is fair.