Re: The changes in the Enterprise-D bridge in Generations...
But for an in universe explanation check out the book 'Rogue Saucer' which took place between season 7 and the movie. The Bridge is severely damaged in a Maquis attack and needs to be refitted. While they wait for that they test out a new Saucer for the ship which can land and take off planets and has extra weapons etc. The Maquis steal this and eventually it crashes too with Riker on board. Very fun novel.
The moral? Never leave Riker in charge.