This is just the game’s meta until they give us some sort of skill based matchmaking or incentivize ‘join any faction’. Good players know when to ‘jump ship’ and change factions rather than suffer a 90% loss rate.
Axis mains are older guys with work and family, they don’t have time to grind events so allies always have golden time during big events.
U.s. also got some good toys to use shifting player base
USA got a new rifle and a new tank and Soviets got a new plane and a new tank in the tech tree. So I guess that may explain why people are grinding allies now.