The hardware doesn't support the relevant security features GrapheneOS requires.

https://grapheneos.org/faq#future-devices

It would take extensive work to achieve the hardware requirements and the capability for an OEM that isn't able to develop their own chips with Memory tagging enforcement (mte) which the Snapdragon 8 Elite used in the upcoming Motorola phones will have. It won't be cheap and it won't be easy.

Google has set the bar high with their security features.

GrapheneOS smearing Fairphone as not secure in 3..2..1..

I wish all smartphones were as easily repairable as Fairphone. The entire battery care stack would become unnecessary.