Maybe they are just tired of getting HO'ed by eL gAy-7's constantly?
Me, I like EW Arena. The planes are slow, fights are usually 1v1, and the clubbing of little baby milk-runner buffs is most satisfying.
Remember folks, a 20mm to the cockpit, otherwise you ruin the pelt.
I also happen to think your perception of MW's popularity happens to match up with a LW arena downsizing, and/or reset.
Gamers want to get the best "item" in the game. You take an "item" away, or block access to an arena that has the "item", they will settle with an arena that allows the next "best". This is what is happening when MW gets popular.
"LW arenas are full I can't fly my eL gAy-7/Spittoon/P-51, so lets go to MW."