A secretive billionaire who backed Robert F. Kennedy Jr.’s presidential campaign donated $50 million to a super PAC supporting Donald Trump the day after the former president was convicted in May of 34 felony counts in his New York hush money trial, according to a report. The huge donation from Timothy Mellon, an heir to the wealthy and influential Mellon family from Pittsburgh, Pa., came as the PAC, Make America Great Again Inc., had only $34.5 million on hand at the end of April, the New York Times reported. Mellon’s contribution made up the lion’s share of the $70 million the super PAC rais…