Email addressing being recycled is a valid problem and challenge. Many sites use an email address as the main unique ID for customers, yet this email address and the account can expire if not used for a prolonged period, hence being recycled and then re-registered by someone else.
It doesn't sound like this caused your issue. But it is a genuine challenge for large companies like Ryanair and for users who might have registered using an old email they no longer own.
MFA and getting a reset confirmation via your mobile as an example can help people from resetting the password and logging in to see personal information which isn't theirs.
Companies need a way of recycling this accounts and letting people re-register, ideally not having to call a support line.