The two Bush ex presidents benefited from Republican Party establishment support when they got elected- for them to now withhold support for the obvious at least plurality, more likely majority choice of US Republican voters, is a great big FU to American Republican voters! We need to let these SOB's know how we feel about their FU insult to the electorate.
They don’t care about the Republican electorate. To them, the Republican Party is a retainer, and Republican voters are schmucks, to be manipulated into contributing and voting for the people the Bush overlords select for them. When the Republican Party ceases to perform this function, the Bush family is done with it.