There are differences in being "innocent" and "not guilty" and "no probable cause to return an indictment." The latter is what a grand jury returns if there is no indictment. As there is no "double jeopardy" involved in "no indictment retured," nothing stops a prosecutor from trying again if more/other evidence refreshes the case.

Grand juries are unique, in that members cannot be challenged for bias, etc. and replaced. They are who they are, and indeed mirror the attitudes and mores of the community.

Grand jury proceedings are also secret. No matter what, the only persons who know what really was presented to the grand jury are the jury members themselves, the prosecutor and judicial staff working the case. So, there's probably a LOT more to this particular case than ever made it into the press.