GKI didn't exist in 2012/2015, so it was very difficult and expensive for OEMs to support Android for longer. Apple could do so more easily because they control both hardware and software. Google introduced GKI and other related efforts/architectures to address this very problem, which is unique to Arm, Linux and the ecosystem around it.
It's really silicon manufacturer's fault for not wanting to mainline and long-term support their BSP, not Google's.
If a device cant get play certified it cant realistically be sold anywhere in the world except china, so no phone manufacturer would choose a SoC for their phone that was not supported.
It's really silicon manufacturer's fault for not wanting to mainline and long-term support their BSP, not Google's.