This is an overly simplified summary that doesn't describe the objection to mentioning Congress as the only body to enforce the amendment. It was 9-0, but 4 justices made a special declaration pointing that out.
While all nine justices agreed that Trump should be on the ballot, there was sharp disagreement from the three liberal members of the court and a milder disagreement from conservative Justice Amy Coney Barrett that their colleagues went too far in determining what Congress must do to disqualify someone from federal office.
It's a protocol, made with open RFC docs.