I am no expert in the matter, but grip is a very personal thing. It is all about feel for me, and whilst one grip on the club for me might be perfect, for you, it may be totally wrong.
What could be happening is that your new grip has improved your confidence as much as anything else. And with a new batch of confidence comes a cleaner ball strike and ultimately a better overal game.
I am sure someone who really knows what they are talking about when it comes to this sort of thing may shed more light on it, but in my opinion, whatever grip you choose (interlocking, overlapping, baseball), as long as you are implementing it correctly should have very little impact on your overal shot. It is all personal preference :)
Good luck and keep shooting those low scores