The term "joining" irritates me more than it should, because you're correct in asking "What is the value of the transaction?". My guess is that they aren't joining anything, CloudFlare bought the company and is keeping the team.
Sure, but Replicate will probably cease to exist in the near future. So a more accurate title could be: Cloudflare buys out Replicate and transfers staff to internal teams.
That's not a given as well. An acquisition usually involves restructuring the acquired company, sometimes in a way where the original team ceases to exist.