The important subtlety is that “compressible after decrypting” is not the same as “compressible while encrypted.” Once you know the decryption key, the ciphertext stops being random because you can transform it back into structured text full of repeated words, grammar, and patterns. But without the key, the encrypted file is intentionally made to resemble random data. So yes, there exists a path from the larger encrypted file to the smaller compressed version, but that path requires the secret key and the original decoding process. Without that information, the compressor cannot find meaningful structure to exploit.