Doesn't answer 'why,' though. 'Why' is asking for the reason it changed from only ice cream to ice cream and food.
You didn't ask if DQ had changed from ice cream only to ice cream and food. You knew the answer to that. You were asking for the reason they made the change.
The question "why" inherently requires reasoning as a response, though. If the answer had been, "DQs used to only serve ice cream, but the founder wanted to..." blah blah blah, that would be an answer.
I mean, it's not an actual answer. It's just a historic fact.
The actual answer is that diversifying your product offerings gets you more business. People like desserts after eating a meal, so it makes sense to also sell that meal.
That's why I think they'll be the ones to assassinate him. Hopefully Caesar style.