It was Stan’s way of writing. He later moved up to editor then publisher and it became Marvels “house style”.
DC never had one person over story direction. Batman and Superman have always had different editorial direction and virtually separate universe’s. Heck, DC pretty much had the same staff from the beginning of comics through the silver age.
It was DC house style to have no to limited continuity until the Bronze age. Tight continuity was Stan Lee thing. DC, as a company, believed tight continuity impeded good stories. This is still true to a large degree.
I’m not saying it’s good or bad. I’m simply saying the DC style has always been separate silos while Marvel has always been the shared sandbox and that DC trying to go shared sandbox is bucking against their basic story telling nature and part of why the DCU so far stinks. They’re playing against their strengths.