Access to iPhone backup in iCloud older than 180 days…

Hard to determine what happened here.

The new phone will have no backups.

If no iCloud backups were originally configured for the recovered iPhone, then none are performed.

If credentials to the recovered iPhone were compromised, then backups can be deleted.

When backups are configured and running, only the current backup is kept around and older backups are automatically replaced unless manual steps are taken.

Are you saying that when you set up your new phone, the old phone backup was not an option to be used to set up the new device? Backups are retained for 180 days if device backup is turned off. I cannot find anything in support sites saying 180 maximum for devices with backup turned on. It’s possible that the backups are only retained for 180 days.

Then no backup remains.