Earlier quoted context omitted.
You don't "just hook it up to the grid". You have to work with the local utility company or companies to negotiate pricing, SLAs, and safety concerns (eg: shutting off power when linemen are working). Helion's fusion reactors are small enough to fit in a couple shipping containers. The idea is that the units can be mass produced in a factory, then transported to data centers and replace the grid hookup as the primary…
But you do have to compete with grid hookups for pricing in data centers. I definitely buy that there's a market for small power plants that cost too much to be competitive on the grid (in some sense that's literally what generators already are), but I don't see how datacenters are in that market.
You do, unless you sign a contract with a large datacenter operator that's willing to pay above market price for the PR benefit/green energy credits of a working fusion reactor. Which presumably is the point of this.