Could be one of several things but it's not unheard of for politicians to get donations from seeming ideological opponents:

• trying to get West to be a spoiler like how Richard Egan donated money to Ralph Nader in 2004 (Egan was a George W. Bush campaign donor and Bush's ambassador to Ireland)
• simply wanting influence, like how a lot of billionaires will donate equally to Republicans and Democrats
• an attempt to torpedo West's leftist credentials because campaign donations are public, and taking money from a conservative rich guy is a bad look for a leftist candidate. Kind of like a scheme Roger Stone pulled where he donated money to one of Nixon's republican rivals in the name of a socialist organization