Most factories have lots of utility connections to their equipment -- kilovolt mains power, compressed refrigerants, toxic waste outputs which must be chemically neutralized before disposal.

Connecting and disconnecting these utilities requires special skills and doing it wrong has major consequences. Special licenses and permits are almost always required by government regulators.

It's the "HVAC guy problem", writ large.

That's true on grid connections, but containers full of batteries could probably overcome that problem.

Porsche has a 2.1 MWhr battery trailer that can deliver 3.2 MW peak they bring to electric track days to keep all the cars charged. That's enough power for some serious industrial processes, and if more is required horizontal scale is pretty simple.

A quick trip overnight to a high powered car charger could fill the batteries by morning. For many loads a simple grid connection constantly trickle charging would be enough power to operate indefinitely.