And Apple management would be stupid to pay $20.5 billion for Tesla's plant, property & equipment. They may acquire an interest in Gigafactory but that's not worth $20.5 billion.
And let's not forget Tesla's largest shareholder is Elon Musk, who went on record to explicitly disparage Apple and its employees not too long ago. Do you think he would sell his beloved company to Apple? https://www.theguardian.com/technology/2015/oct/09/elon-musk...