I've heard that diesels can actually suck lube oil up from the crankcase
and run away, but that'd come from worn seals or piston rings.

Thanks,
Rich

Many diesels are turbocharged. If those seals fail, the engine ingests
it's own lube oil and revs itself to destruction.
It sounds like these diesels were running on the well gas. The normal
engine governers would have shut off the fuel as soon as the speed
increased. There are only two ways to stop this overspeed. 1) increase
the mechainical load on the engine. This can be done in a car but not
on a generator like these. 2) shut the air intake to the engine.
That's also just about impossible on engines as big as these unless
there's a system in place to do it.

John