you might be right because this happened to me just now when i installed 2.0.2 update. so in case if a newer version beyond 2.0.2 releases from now, i still don't how to go back to the older version? I don't want to have to delete everything & reinstall again because i did just that & now everything is working on 2.0.2 again. Currently reinstalling the Torna expansion since that was updated too.It happens because newer version of DLC is encrypted with different key and when at launch game checks DLC it fails at decryption and crashes. In this situation you can try downloading older version.
Also you can check if keys is correct by using 'NCA-NSP-XCI_TO_LayeredFS_v1.4' tool:
First extract NSP, then choose 'Info Ecrypted NCA'. Error at the end means key is wrong.