I think some of it is down to WB wanting Batman confronting Superman, the death of Superman, and introducing Wonder Woman to rush into JL all in one movie. At least I remember fandom discussions indicating that these were all beats he had to hit from on high, he had to make a 3 hour movie to fit it all in, and then they forced him to cut it down for theaters.
Though with the unveiling of the original 5 film plan, maybe it was all his idea.