Kushner has a much different purpose, which would be compromised if he allowed himself to be associated with the Trump madness.Kushner was in the Middle East when the Trumpies attacked the Capitol, but I don't believe he was unaware of Trump inciting mob violence the five weeks prior. Maybe he couldn't believe Trump would go so far.
He may have thought that he would be better insulated from it if he was out of the country.
He's a spokesman for the ME's apartheid regime and that requires him to be on friendly terms with the Democratic party.