Reading between the lines, my uneducated guess is that Sable knew they were going out of business either way and had to chose between paying ALL of Cloudflare's

Reading between the lines, my uneducated guess is that Sable knew they were going out of business either way and had to chose between paying ALL of Cloudflare's legal fees (possibly in the millions) or paying a token amount and giving up their (now or soon-to-be worthless) patents. The latter results in fewer financial loses for Sable and makes for excellent Cloudflare PR. Edit: Also, it's entirely likely that Sable still made a tidy profit overall when it settled with the other big networking companies and decided to quit while they were ahead.