Why might people not believe Billy Foyle's point of view about 'Mary Celeste'?

Alcoholism, imagination and the desperation of poverty are reasons why people might not believe Billy Foyle's viewpoint about the half brig Mary Celeste. William Foyle claimed to have fallen asleep aboard the hermaphrodite brig and to have severed the lifeboat's 330-yard (301.75-meter) tether when the Mary Celeste Ten (of captain with daughter and wife, three officers and four seamen) abandoned ship because of the volatile cargo of 1,701 industrial alcohol-filled barrels marking sounds prefatory to mass explosions. He purported that Captain David Reed Morehouse of Dei Gratia secreted him to Gibraltar, for subsequent passage to England, in order to claim salvage on the derelict, yawing part barkentine part schooner Mary Celeste.