Their latest cult belief, proscribed by their masters, is that IF the Bidens did something that would excuse trump's crimes.
That's a common logical fallacy that is especially prevalent with the Right.
IF someone on the other side did something, then it's completely within bounds for everyone/anyone on your side to do it - even if it's illegal, immoral, unethical, or corrupt.
That's the moral equivalency that the Right has come down to in order just to keep power, the country be damned.