It isnt quite normal circumsatnces.
The ashes is the biggest series + England won it for the first time in a long time + Australia are the top team to beat for anyone + the last series was incredibly tight and hard fought + the return series was scheduled for just 1 year later + massive public interest in that series from both sides, not least Australia where they consider it the biggest summer of cricket in their history.
Perhaps the ashes scheduling should be considered. technically its every other year, but in reality it varies from 1 year to 2½ years.
Even so, I cant see that its all about the ashes. Pakistan will play to full houses in england, something they probably dont do anywhere else.
There is, though, probably a growing apathy towards ODI cricket, but inst that just a cause for celebration