>why Netflix didn't use a POWER machine for its higher memory throughput.
Probably because there is no POWER9/10 option available from AWS and Netflix is a heavy user of AWS.
Probably because there is no POWER9/10 option available from AWS and Netflix is a heavy user of AWS.
As evidenced by their heroic efforts to tunes performance[2], and their careful choice of hardware[3], they could certainly deploy POWER if they chose to.
[1] https://openconnect.netflix.com/en/