I think it was a short snippet of a longer interview to follow, but similar to above, the main three reasons for me were:
1) Club on the up, wanted to be part of it
2) Gus very enthusiastic about him coming to Brighton
3) Brighton gave him space and time to consult and speak to people about the decision, which he 'really appreciated'.
So made him feel wanted, and treated him like a grown-up, then.