One of the main reason EPL generates so much revenue is through tv broadcast, especially in Asia. Even middle level clubs have fan following because people can watch almost all the matches. So when there's no big club match, people would still have to watch Swansea vs Cardiff since no other league match is on at that time. Most of the liga matches happen after 12.30 in the night or even later. When the liga authority realizes this and changes the time a few hours earlier to accommodate Asian viewers, they can generate millions of euros in tv rights. I'm not talking huge changes, just moving many of the matches by a mere 3 hours before would do the trick.
I bet that the tv spectator population of Barca-Atletico wouldn't be even half of that of Arsenal vs Spurs.
I don't know... The EPL is already well "established". Few people watch La Liga here, and it doesn't have anything to do with the time of the matches. Why would an Arsenal supporter stop watching his team?
EPL has a number of "big" teams: Man Utd, Chelsea, Arsenal, Liverpool, City. Matches with those teams will draw more spectators than any La Liga match bar Real-Barca. Part of the reason for this has been the way Barca and Real have been steamrolling opposition over the past seasons.
On a side note, for people with no TVs here, we don't want La Liga matches to show at the same time as BPL as there would be no chance of La Liga match prevailing over BPL in a bar/restaurant.
This is all based on my own experience. I have no idea how it is in Asia.