Well they're veterans accustomed to earning or losing big money on film ventures, so maybe they do know best - maybe most everyone will be surprised and JL will be a huge hit. But even as an outsider I can't imagine this is a wise decision when so much money is on the line (including interest in merchandising, bluray/DVD/streaming sells, etc). But what do I know, I'm just some dude.
On trusting Snyder to change gears effectively, I can agree with them in some ways. One of my favorite films is Snyder's Dawn of the Dead remake, and that was largely character driven and, I think, defined by its colorful cast of characters and their often humorous interactions and growth together. When I think about that film I remember the quirks and personalities of each character, memorable moments when they clashed or bonded, and how they all ended up by the conclusion - together. There was even some of that in 300, though on a much smaller scale - and I enjoyed 300 too.
It's just after some reflection on MoS and BvS, and a rewatching of both, I can't (edited from "can", typo) see Snyder turning the ship around within the particular world he's working in. But I am hoping for the best. The man directed one of my favorite movies, I love DC, and who wouldn't want to see JL shine?