could be wrong, but my understanding is that it is fundamentally...

could be wrong, but my understanding is that it is fundamentally cheaper and more efficient to import the inputs of steel (in this case iron ore, biochar etc) and produce it domestically than it is to import the final product from a foreign producer.

Helps that several of KSA's busiest ports are located on the Red Sea (one of the busiest shipping lanes - thanks Suez), so demand can be serviced easily. Houthi shenanigans aside, KSA has a range of advantages on that front.

Also understand that similar projects (see Essar Ras Al-Khair steel plant) are located on the coast - so water access is no problem.

the steel produced is intended to meet domestic demand as KSA transitions towards a post-oil (and relatively green) economy, so market access is a non-issue.