Why Is Luke's Book Ending This Way?

Many scholars have suggested that the book's abrupt ending has implications for when it was written. We get no resolution on what happened when paul appeared before nero. This is all the more striking because whatever happened would have suited luke's purpose. If paul was acquitted at the trial, then luke could portray paul and the gospel as being gloriously vindicated. Yet luke gives us neither of these endings. And the only reasonable conclusion is that he didn't tell us what happened to paul because he couldn't - the trial had not yet taken place.