Freddie and Carly simply would not have worked. Freddie had put Carly on a pedestal pretty much the whole time they’ve known each other, no one can live up to expectations that high. Also, while they were very good friends it was clear that Carly was not interested in Freddie romantically at any time. Freddie and Sam had this nice banter between them, yes sometimes Sam’s insults went a little far but overall it seemed playful. And then when you find out Sam has never kissed a boy and Freddie has never kissed a girl you just really want them to be happy.
At the end of the day though I always thought Gibby would end up with Carly.