GrapheneOS currently has like half a million users and growing. And many of those users would love to not be forced to have a Google Pixel (even if those are really good phone).

The question for Motorola is: "given the cost of meeting GrapheneOS' requirements, how many more devices will we sell?". Hundreds of thousands of devices is not nothing, I guess. Plus they get free consulting from the team building the most secure phone OS out there.

I really don't understand why smaller smartphone manufacturers didn't fight before for that. Say Fairphone: I don't know about today, but a few years ago they finally got profitable by selling something like 200 thousands units a year. If they had designed a phone to be supported by GrapheneOS, that would surely have increased their sales quite a bit. Now that ship has sailed, GrapheneOS will be focused on Motorola for a few years.