By 2021, Quest’s (last seen around version 12.x) was no longer actively maintained and only available as 32-bit. The company shifted to a "Toad Edge" product for open-source databases and a commercial-only model for full Oracle support. If you found a site advertising "Toad for Oracle 64-bit 2021 free download," it was almost certainly an unauthorized copy or a time-limited trial.
If you don't have a full Oracle client installed, you can use Oracle Instant Client: download toad for oracle 64 bit 2021