got this from a comment on reddit

It wasn't accidentally bombed. the survivors very much agree on that and the testimonies. Other than that the huge american flag was there, and it was bombed repeatedly and not only once.

The motives aren't agreed on, some say it's because they got intel to the https://en.m.wikipedia.org/wiki/Ras_Sedr_massacre or a massacre in gaza. At least that's what james bamford think, Or they made it to be a false flag operation were Egypt attacked so usa joins the war.

James Bamford, an author that has extensively chronicled the history and operations of the National Security Agency, posits that the massacre may have served as a casus belli for the Israeli attack on the USS Liberty. Bamford theorizes that the Israeli Defense Forces were concerned that the USS Liberty, a signals intelligence collection ship, may have collected evidence of the massacre and was thus attacked in an effort to suppress the evidence.[9][10][11][12][13][14]