Whatever the factors, the success has them expanding the number of games and seriously discussing a franchise there.
I have family over there and some of them are totally NFL daft and aside from the few evening games (evening over here) they have no problem watching live NFL on their TVs. The 1 pm kickoffs are at 6 pm over there and the 4 pm kickoffs are at 9 pm.....so they don't need their pvrs for those.
The beauty of London is that it is easy to get to from all over the UK and they are really drawing from a market of 60 million or so. If you look at Green Bay and realize it is a regional team that draws from afar....London is Green Bay on steroids (probably not an analogy they use at the NFL HQ).
A team based in London would not only let them tap into the Euro market/money it would probably produce a pretty big boost to their domestic tv money too. 8 games a year would be played in a time zone that would allow them to have, say, 3 pm local kick offs that would mean a 10 am (eastern) kick off...allowing them to sell the networks on games on Sunday starting at 10...leading into their 1 pm kick offs...leading into their 4 pm kick offs..etc. Networks would pay a lot more for the rights if they could squeeze in another live match on Sundays.