I have very dumb question but i've always been a baby when it comes to understanding networking and such

If I buy a domain, I know I technically just rent it from a registrar company, and some of the money goes as fees to ICANN, right?

But why does that middleman company exist in the first place? Why can't I just directly pay ICANN for the domain? :thonking:​ Did the registrar companies just preclaim a bajillion domains or something?

Edit: thank you for all the answers everybody 💗