What I’m confused about is how this wallet even exists when I’ve made it offline. How is a wallet generated?
Every single bitcoin address which will ever exist (excluding new address types which may be created in the future) already exists. Anyone can send bitcoin to any address they please at any time, whether or not someone controls it or it has ever been generated by a piece of software before. When you generate a new address using bitaddress, you simply generate a random number between 1 and (just less than) 2
256 which is your private key and allows you to "unlock" one specific address.
This address can create raw transactions and broadcast them as both actions require internet connection
Being pedantic, but this isn't strictly true. All you need is a way of knowing which UTXOs are present at that address. The most obvious non-internet way of doing this is via Blockstream Satellite (
https://blockstream.com/satellite/), which will allow you to sync a full node without an internet connection, but you could also receive blockchain data over a local network, via a USB drive, or any other way of communicating data. You don't even necessarily need the latest blockchain data - provided you know the relevant UTXOs, then you could create a transaction manually and sign it with a private key, all without having an internet connection. There are also a couple of ways you can broadcast transactions without an internet connection, although these are more difficult to achieve than creating transactions without an internet connection.