My guess is "that they did the math" and had an engineering study which convinced them that getting AI datacenters into space will make sense.
It's also not hard to imagine why, the process alone once perfected could be reused for asteroid mining for example, then mirogravity manufacturing, either of which alone would be enormous capital intensive projects. Even if AI dataenters in space are break-even it would be a massive win for SpaceX and leave their competition far behind.
There is no benefit to putting data centers in space versus the giant cost that you would incur by doing so.
Can people please try and use their fucking brains for a second?
Have you considered that people smarter than you think it is plausible?
I know many people smarter than me, plenty of them who have spent careers building data centers, and not one of them think this is plausible.
You should consider whether people smarter than the average investor are pulling a fast one.