A decision of this magnitude doesn't get made without, if not the behest of ownership, then minimally the approval. Harrison is the fall guy for a collaborative effort, including the PR nightmare.
To be clear, he's far from blameless for not maxing out the return (should have been Reaves and the Lakers second unprotected 1st, with Gafford going the other way).
Their MAGA owners seem to know little to nothing about the league, so I don't think they knew the caliber of asset they had at their disposal and just decided they weren't Doncic fans and didn't want to pay his looming $345M extension.