Because both are languages that could feasibly be used to solve a particular set of problems. TigerBeetle could have been written in either, they explain why th

Because both are languages that could feasibly be used to solve a particular set of problems. TigerBeetle could have been written in either, they explain why they didn't choose Rust but it was a feasible alternative (in a way that Java or Python would not have been). Conceptually C and C++ are also in that potential solution space, but I'm sure they feel that Zig's properties are superior for what they want.