1) What Radium app? I couldn't find an app called Radium in the App Store.
Raydium, as it pertains to crypto, is a platform used to enable crypto exchange trading.
Ostensibly, even if there was a Raydium, it's only providing access to the exchange, and there's nothing (at least not much) nefarious in that.
If you lost your funds it's likely either a problem with your wallet, or your account was somehow compromised and someone got access to your funds. In this context, it's the same as some nefarious user guessing your PIN and draining your bank account - while they might sympathize, it's not exactly Apple's fault just because you installed your bank's app on your phone. It's an issue to raise with the bank (or in this case your wallet provider or the exchange).