How could I have been eligible for Airdrop #2?

Any wallet, old or new, was able to take part in Airdrop #2.

To be eligible, a wallet needed to be holding a balance of at least 500 XLM (or yXLM) & at least 1 AQUA at the time of the snapshot.

Your reward calculation was based on your XLM, yXLM, and AQUA holdings in your wallet.