How would there be less competition in that scenario? If Android would be restricted to Google Hardware the market would look way more diverse with Samsung/HTC

How would there be less competition in that scenario? If Android would be restricted to Google Hardware the market would look way more diverse with Samsung/HTC rocking their own solutions and Nokia/Windows still having market share. The same if Android licensers were more free to provide their own solutions (see what Amazon did with the Fire brand) instead of forced to bundle Googles services on every device.