"Hey, everyone else is in the golf market. Why don't we jump in too. We make shoes!"
Companies creating line extensions "just because they are in a related segment" doesn't always drive the best outcome, especially when you come up against the big boys. In many ways, the move makes perfect sense, since NB brand is sold in a very limited way, so they can control this launch to some extent. But it will be VERY expensive for them to break into green grass locations and other retail, and in all likelihood they will be forced to buy their way in.
It's not really bad news at all. It makes a company like FJ, who is very focused on the golf only market, stay their course and continue to tell their story about how and why they are the market leader. Many come and go. The strongest and smartest survive.