I guess you were downloading something else and using all your upload bandwidth. When you disconnected and reconnected, it broke the other download. So VG had more capacity to respond when packets arrived. (IP needs to send confirmation).
Or your ISP was throttling your connection. The disconnect was enough to reset your counter, so you got more capacity.
I think really it just goes to show that there are many variables, any one of which could be the cause and it can very difficult to know for sure.
I know going to your profile from EU to US (or back again) can get you a different server which may help the speed. But see my post on todays releases, a different server may not have the content you want.