Sam is not alone in his construction. He did the first step which is making the concrete slabs on his own and he would need to continue doing so. But the rest of the work could be left to someone else.
For example, his shadows. Even though he can take his beasts out too, he is not exactly comfortable with that hidden observer breathing down his neck.
As for why he is not going and dealing with them directly, he was waiting for the word from Raunak about the involvement of his future father-in-law. He wanted to know this information to decide on his approach.
If he was not involved, he would have just dealt with them and be done with it. But now that his involvement is there, he would have to think of a different way. He has to make sure that his message goes through.
Even if this group of people particularly didn't come from that guy, he would make use of them to give that message.
