We're talking a little bit about different things.

Because of expenses, Commies need to sell their units on the market every 50-100 turns. It is very common for Commies to "double sell" every day on other servers. Problem is, turns comes in so fast on Express that you often end up with 2X or 3X turns to spend when you login, to compensate, they increased the maximum % you can sell. With the default %, you would literally be forced to babysit your country every 2 hours instead of every 6 hours to be playable. So when you wake up overnight with all that turns that you can't spend because you need to sell first, you need to sell 3x every 2 hours to catchup on the turn rate.

Commies dominate on this server because of a different reason: Game length. Express runs on a total of 1800 turns, every other server has over 3000 turns. The shorter the game length, the better Commies are, because again expenses. Expenses formula isn't linear, it grows exponentially with NW size, which means Commies are actually the worst countries to run on servers with long game lengths (eg Alliance with 4320 turns). 1800 turns on Express means that the typical land sizes countries grow to are small enough that Expenses does not become a problematic factor for Commies.