I know that when a certain global HVAC company brings in a new "fresh" class of salespeople, they bring them in all at once about 20 to 30 at a time. The will go through weeks of training. Some make it, some don't.

The majority, if not all, of the incoming (just of of college) class did not major or obtain a degree in anything sales related (business, management, accounting, marketing, etc.). Most of them graduated with mechanical engineering degrees. Why? Because it is easier to train and teach someone how to sell than it is to teach some the technical details (physics) of HVAC systems. It is also easier to sell when you know and understand the product you are selling. Most of the units sold are custom built for the particular building they are being used on/in.

Likewise, it is easier to train or teach someone a new programming language than it is to change or modify someone's attitude and personality.