How would Sollecito (or anyone, for that matter) be able to grab the hook of the clasp while the bra was still being worn. The hooks are covered by material. All the evidence suggests that whoever removed the bra tried to simply pull it apart by grabbing the material either side of the clasp area. The bending of the hook supports this. And, as Charlie has mentioned, it may well be that the material near the clasp actually tore free, rather than being cut free. If so, this lends even more weight to the theory that someone pulled very hard on the rear material near to the shoulder straps (making the hook bend), but that the material ripped before the hooks failed.
Anyhow, regardless of whether the bra tore apart or was cut apart, there's no reason why anyone would have been placing their fingers onto the hooks themselves. If they had indeed bothered to lift up the flap of material to expose the hooks, they would have seen how the hooks engaged, and would have removed the bra in the conventional way - by pushing the two sides together to disengage the hooks. The very fact that the bra was instead either ripped or cut open strongly indicates that whoever removed it never got as far as examining the hooks.