Bringing in some bigger, tougher guys wasn't done to hinder the young players development, but actually to protect them. And for Dolan to protect his $13 million/year investment in Panarin. And other Rangers as well who aren't that big like Fox, etc. The Rangers have developed a skill team already. They needed some muscle to balance it out.
Yeah, Dolan is known for having a short fuse but he hadn't messed with the Rangers like he used to do with the Knicks. That is, until the Tom Wilson incident and his open letter to the NHL. I feel as owner of the Rangers, it was appropriate for him to do so.