Pedal and Cassette Shake
I can't see anything wrong at all.

The any vibration you may feel when the rear wheels is spinning but the cranks and chain and cassette are not moving is due to the clicking of the pawls in the free-hub.

I think if you hold a pedal and spin the cranks so the rear wheel turns you will not detect any vibration or 'shaking', as the free-hub will engage.

I think if you ride the bike you will find it functions normally.