I think it happens with two ways firstly the man who made the question he can mark any answer as the best answer and the second way is the the Google maps automatic filters who mark an answer is best based on its content. @SebaasC please mark my answer as a solution if you satisfied.
This is a useful feature but it is not new. It is available for more than one year and a half ago and I mentioned it here.
As @Muhammad_Usman mentioned it is possible both bythe selection of the person who asked the question and also the system detection based on the relation of the answer to the question and thumbs up but after availability of this feature, fewer answers mark as the best answer by the system, although in my experience people also use this necessary feature much less than expected
That’s not a silly question at all. Sometimes we have some doubts about one thing and asking our friends will address us better. This is so acceptable thing, especially in the intimate atmosphere of Connect.