Jim you have to look at it from the station managers point of view. He is in charge of making sure the station makes money...it's a business just like any other. It's a policy that is dictated to him from above. The station may be owned by a chain or locally owned...does not matter. Local newscasts are a cash cow for any TV station. Affiliates do have the choice not to air certain programming if it will conflict with their local programming in certain markets. It's a balancing act...do I air this network program which will very likely run into my local news where I make tons of money or do I make tons of money...not a very hard choice for him anyway.
To answer why he would air a network game with no local interest and preempt the news...perhaps he had some local sponsors for that particular game, who knows. Undoubtedly, he had some way of making up the cash he lost for not airing the local news.
The viewing public usually does not agree with the stations policy, nor do they understand it. The only thing they know is the program they want to watch is not on.