Especially because if they had read about or studied this problem they would find tons of prior art where CRC32 was considered not secure for solving the problem. CRC32 solves a different problem -- how do you verify that the data that was received is identical to the data that was sent. It makes no guarantees about who is sending the data, which is the real problem signatures solve.

More specifically, it solves the problem of verifying that the data received was not accidentally corrupted somehow. Unlike cryptographic hashes, CRC32 does not do much to defend against deliberate, malicious modification. It's too easy to craft some different data that matches a given CRC32 value.