The object of criminal proceedings is to establish guilt or innocence. The fact that Flt Lt Williams was acquitted does not mean it was wrong to bring a prosecution against him in the first place. Sometimes, the only way to determine matters of such gravity, to the satisfaction of all those affected, is through the courts.
The last two years must have been very traumatic for Flt Lt Williams and his family. He can, however, draw comfort from the fact that he has, very publicly and emphatically, been absolved of any responsibility for this tragedy.