Attempt to reword the complex if

crates/matrix-sdk-crypto/src/types/events/utd_cause.rs

@@ -217,19 +217,24 @@ impl UtdCause {
      * ```
      */
     fn determine_historical(crypto_context_info: CryptoContextInfo) -> UtdCause {
-        let backup_exist = crypto_context_info.backup_exists_on_server;
-        let is_backup_configured = crypto_context_info.is_backup_configured;
-        let are_we_verified = crypto_context_info.this_device_is_verified;
-
-        match (backup_exist, is_backup_configured || are_we_verified) {
-            (true, true) => {
-                // Either backup download is working but we still don't have the key, or backup
-                // download *isn't* working despite being verified. In either
-                // case, we shrug and give an `Unknown` cause.
-                UtdCause::Unknown
-            }
-            (true, false) => UtdCause::HistoricalMessageAndDeviceIsUnverified,
-            (false, _) => UtdCause::HistoricalMessageAndBackupIsDisabled,
+        let backup_disabled = !crypto_context_info.backup_exists_on_server;
+        let backup_failing = !crypto_context_info.is_backup_configured;
+        let unverified = !crypto_context_info.this_device_is_verified;
+
+        if backup_disabled {
+            UtdCause::HistoricalMessageAndBackupIsDisabled
+        } else if backup_failing && unverified {
+            UtdCause::HistoricalMessageAndDeviceIsUnverified
+        } else {
+            // We didn't get the key from key storage backup, but we think we should have,
+            // because either:
+            //
+            // * backup is working (so why didn't we get it?), or
+            // * backup is not working for an unknown reason (because the device is
+            //   verified, and that is the only reason we check).
+            //
+            // In either case, we shrug and give an `Unknown` cause.
+            UtdCause::Unknown
         }
     }
 }