Still... how is it possible that a seed can't be brute forced if there are so many addresses out there and so many wallets? Example with electrum and nano ledger s, waves, myetherwallet, bitcore and all of those? But are the word seed list for those other wallets like waves and myetherwallet the same as for electrum/nano ledger s?
An Electrum seed is not the same as a Ledger Nano S generated seed. Ledger generates BIP39 seeds, Electrum doesn't. They have their own standard, however, Electrum also uses the same wordlist as other BIP39 seeds. Just by looking at a 12-word seed, you wouldn't be able to distinguish a Ledger from an Electrum-generated seed.
Any words that belong to the BIP39 words list will generate a wallet with addresses. You can try it yourself. Open your Electrum > click on standard wallet > click on I already have a seed > open the options menu and tick the BIP39 options. Now enter any sequence of 12 words and click on next. Electrum will generate a wallet based on your entries.