Not sure which specific trim pieces you're talking about? But I found a number of them are tricky off, and tricky back on. Maybe if I did this repeatedly it would become easy, but as a one off experience I went in expecting it to be a PITA.
FWIW, when I did mine there was some trick to getting the clips engaged properly. When they were not fully engaged I would describe the look like you do above, and they looked noticeably off. So based on that I'm fairly confident you haven't actually messed up the molding itself. Almost certainly you just need them reattached properly.
Not sure I can describe exactly how I did it, but after playing with them a number of times and noticing that they were still not all the way in I continued to try and reseat them until I got it right. Best way I can describe it is to work to align the entire piece before trying to fully engage the clips. I found that if I engaged the clips starting at one end, then often at the other end it wouldn't align and so those clips wouldn't engage right, and it was then too tight to slide it around to get it to fit right. Once I got the hang of it though it got easier, so stick with it...
Good luck..