One possible reason was that the calabrian revolt started before any british landing, and that both Stuart and Court of Parlermo could hope a kind of Sanfedist revolt. See the chronology in my other post.
Beside, to leave Gaeta to its own, and capture some forts of 50 to 250 men's garrison (source : Digby Sata book) did not help much keeping the French far from Sicily, they were back at Reggio in march.