God releases Paul from jail in Philippi so he can grant salvation to the jailer and his family

The importance of this story is to convey that there is a stark difference between the ways Jews and Gentiles get saved under Paul’s new Gospel. In Acts 2 the Jews ask how “we” as a nation can be saved. In Acts 17 the jailer asked how he, individually, can be saved. It’s a different program, a different Gospel, a new way of being saved offered to Gentiles individually.
The Jews were God’s chosen people corporately.
Now, You are God’s chosen person individually.