It makes sense.  The 49ers take Eric Reid-FS with their first round pick.  Reid replaces starting free safety Dashon Goldson who left via free agency.  If they take Zach Ertz at #34, he replaces Delanie Walker who also left via free agency.  In the 49ers two-tightend heavy offense, they need a second tightend.  Then with their second, 2nd round pick, they select defensive linemen Jesse Williams who can play both nose tackle, and defensive end in the 49ers 3-4 defense.  Starting nose tackle Isaac Sopoaga left in free agency, and Williams not only could replace him as the starter, he would provide depth because he can play both NT and DE.

Reid, Ertz, and Williams alone would be an outstanding draft.  They are all three likely day one starters.(Ertz from the two TE package).  But of course the 49ers have more selections to come.  Very nice!