They probably were struggling for a good story since it`s been since 2012 that we last saw Shaw and David head of to Paradise, and they realized that there is no other way but to do it now..
And i wonder if it will be a slow progression like will we just a little in this one and then the full connnection in third or fourth film.
Also will he introduce Ripley and the Nostromo picking up the signal, and it ends where Alien begins, and also we don`t know how long that ship was stranded there before they come along.