According to your profile, you have cross-saved from PSN to Steam, not the other way round. In any case, switching any linked accounts when cross-save is active is not possible. I'd recommend first contacting Steam support whether it would be possible to recover the account. If restoring the account is not an option, you will first need to disable cross-save, unlink the account you wish to remove, link the account you wish to add, wait out the 90-day security lockout, then reactivate cross-save. If you are unable to disable cross-save, you can use the from at the bottom of the following article to send Bungie a request to do so: https://www.bungie.net/en/Help/Troubleshoot?oid=48099