Armand Hammer wasn't the CEO, just a minority shareholder and board member. He wanted to buy the company because he liked the name and apparently already used an arm and hammer as his personal insignia. (Fun fact: His grandson is Armie Hammer, the actor, who was named after him.)

I notice that in my home state, the head of more than one auto dealership had the same last name as the brand of car sold by the dealership, for reasons that were coincidences.

I wonder if there is some kind of unconscious social bias at work in these cases?

If your name matches a brand of a car it might be rational to sell that brand; assuming it's otherwise a completely arbitrary choice, it probably helps name recognition and memory, since some customers will probably mention it as a mildly interesting anecdote to their friends and family.

en.wikipedia.org/wiki/Nominative_determinism