Why did Sic Mundus not use the machines?

Major spoilers ahead.

The members of Sic Mundus arrive in 1888 with the machine. They run out of fuel and try to find a way home.

Later alt Martha arrives, giving them the needed fuel. But instead of using it with the machine and try to return to home (what at least was the intention of Adams followers at first), they try to build their own "Sphere" from it.

Even later Hannah arrives with another (operational and presumably still fueled) machine. It seems unlikely she took a "one way trip". So now Sic Mundus should have two operational machines, one still fueled. But it seems that at that point in time they managed to get their "Sphere" working anyway?

So my question is, if they had a machine and fuel, why didn’t they use it and instead stay there for some other decades?