When I smooth my mesh, Maya seems to add edge loops instead of properly smoothing my mesh. I added some images, the first being the unsmoothed mesh, the second being the smoothed mesh I see, and the third being the way the smoothed mesh should look.
I'm following a tutorial with a similar model and ngons and their smooth preview looks fine. Mine seems to add extra loops/cuts while theirs smoothes out fine despite our models being roughly the same.
I made a really rough mesh in the same scene and it smoothes out without adding in extra loops/cuts. I looked at the attribute editor and everything seems to be the same with both the original and rough mesh, despite the smoothed preview looking very different. I'm assuming I just clicked something that changed the mesh preview for the original mesh but I can't seem to figure out what it is.
I added images of the original mesh and the rough mesh I made in the same scene to show what I mean.
As I had said before, your mesh is not clean and has Ngons, you have 2 vertices on top of each other, if you enable Display>Heads up display >polycount you will see that.
Just use the merge vertices tool to clean up the mesh.
