keychain passwords wont transfer to new iphone 15 Pro Max

Perhaps a study of how to create new KeyChain and passwords may help?

There are some ideas and of those, some are workable; sort of..

This might begin with the wording of a search such as:

https://duckduckgo.com/?q=make+new+keychain+passwords+iOS&t=ftsa&ia=web

Automatically fill in strong passwords on iPhone - Apple Support

//support.apple.com/guide/iphone/automatically-fill-in-strong-passwords

This suggests How To's: Such as "automatically fill-in a saved password"

and also how "prevent iPhone from automatically filling in old passwords."

Make your passkeys and passwords available on all your devices with iPhone and iCloud Keychain - Apple Support

How to Setup iCloud Keychain and other things, this is viewed as an option.

Either use or restore lost keychain function from the Cloud across devices.

Find saved passwords and passkeys on your iPhone - Apple Support

//support.apple.com/en-us/HT211146

"Learn how to find and edit your saved passwords and passkeys on your iPhone or iPad."

"Note: If you enter your iCloud Security Code incorrectly too many times, you can’t use

that iCloud Keychain. ~ You can contact Apple Support on the Apple Support website

to verify your identity and try again. After several incorrect attempts, your keychain is

removed from Apple’s servers, and you need to set it up again.

To learn more about iCloud Keychain, see the Apple Support article Set up iCloud Keychain."

Keychains and passwords; some differ a little between macOS & iOS.

Each system has some rules; over time, these have drifted somewhat.