Nonetheless, I doubt that the xAI datacenter had such footprint constraints that it really needed the smaller jet engines. Perhaps the time-to-delivery for really big Diesel generators was too long, so they opted for the already available repurposed jet engines.
The efficiency of the generators with jet engines could be increased a lot if the heat from the exhaust gases would be recovered and used to generate extra electric power, with a steam turbine or with another kind of turbine with Rankine cycle, e.g. with organic vapor.
I'm guessing most gas power plants use the combined cycle, otherwise you'd be wasting the energy of the exhaust gases. That uses a steam turbine heated by exhaust gases from the gas turbine. https://en.wikipedia.org/wiki/Combined-cycle_power_plant
But they do have certain drawbacks, and may not be the most EFFECTIVE for a given application.
You do have to look at a long list of constraints and use cases.
And sometimes, time to market is the most critical factor so you take whatever you can get your hands on. Which xAI has repeatedly proven that they will do, regardless of the environmental consequences.
I remember doing the math for small power generators and the math didn't work out for small turbines until the diameter of turbine went up in size, before which a diesel engine was better. But when scaled up, turbine generators were rapidly making up and surpassing diesel generators.