At almost every single online simracing series, we have the same old story, no matter the title, no matter the adminning team, no matter the drivers: attendance is good the first few rounds, then it drops significantly around halfway.
It's very frustrating for drivers and admins alike, makes the racing tedious quite quickly, and makes championships look quite irrelevant.
So what about keeping things as short as possible? Maybe something like 3, 4 rounds championships. Or maybe even more single events(the 2H race format has always worked well over the years).
As they say in show-business, always leave them wanting more...