Proof of stake with too few nodes and a exploit on their bridge allowed this to happen. They have pledged to make everyone whole The Ronin team explained:
"Five validator private keys were hacked; 4 Sky Mavis validators and 1 Axie DAO. The validator key scheme is set up to be decentralized so that it limits an attack vector such as this, but the attacker found a backdoor through our gas-free RPC node, which they abused to get the signature for the Axie DAO validator. This traces back to November 2021 when the Axie DAO validator was allowlisted to distribute free transactions. This was discontinued in December 2021, but the Axie DAO validator IP was still on the allowlist."
As for Crypto.com... their marketing is HUGE... their fees high. I own some CRO and farm on there as well but https://www.harmony.one/ is cheaper and faster and is where many games go to launch because of this
If you haven't got these yet... look into them: Start with coinbase, take their courses get free crypto then download their Pro version... fees are much better than most CEXs and safety is better.