Fastmail requires payment meaning it is very closely tied to your identity. Proton is one of the very very few who do not tie a new email account to your identity via phone number, payment info or alternative email (which requires phone, payment info etc..).

Even proton only provides webmail free - pop3/imap/smtp require payment. But that's still better than 99.99% of other webmail - everyone verifies via some method that ties to your personal info.