You guys think up better plot lines than I do.
Hood was first an Irish peer, so that's probably why he knew of Kingsdale. It was quite common for someone like Hood to pull strings for a friend, in this case, perhaps an Irish judge or someone, to help a young peer try and regain his fortunes. And with Granger's reputation for prize money, an appointment to Bacchante would seem to be a good match. I can see other sons of peers (like Clifton) or magnates (like Llewellyn) furious that they weren't allowed to go on this voyage, despite the risks.
As for Maidstone, I think Granger said it best. When guineas and pounds are on the line, all bets are off.