Why compromise the announcement at all though?
If they wanted Souls fans to watch, they could just put a teaser for their conference and end it with a fade up of the fog door. Job done. In hours everyone online would know Sony was announcing a new Souls game.
They didn't need to reveal any of this, which is why I find it extremely hard to believe they did.
As for why we don't have the trailer, the first leak was obviously screen grabs from a low quality stream because it had b-frame artifacts, this is obviously from a source file. It might be the same person, but it isn't the same source file, and I'm sure whoever it is enjoys the attention.
I get what you're saying, that would have worked nicely.
But I still believe there's no such thing as bad publicity. Nobody's going to judge the graphical quality of this game over some gifs with compression. This keeps the buzz going strong and I don't think that is a bad thing necessarily.