and that the scenario that they're viewing is if each of those individuals were impeached for, or convicted of, treason. Conviction of the President would not negate the VP. From 538.com:
"Another possible crisis that would fall into this category: impeachment. It doesn’t come up all that often, but one source of constitutional confusion is the impeachment clause in Article II, Section 4, which states, “The President, Vice President and all civil officers of the United States, shall be removed from office on impeachment for, and conviction of, treason, bribery, or other high crimes and misdemeanors.” What are “high crimes and misdemeanors?” The nation debated this during the Clinton impeachment but didn’t really get any closer to a definition. Since there’s little agreement about the conditions under which a president can be removed from office, we might be in for a constitutional crisis if the House attempts to initiate the impeachment process. Then again, maybe not. The criteria are murky, but the process for removal is clear: If the House drafts articles of impeachment and the Senate votes to convict, the president is out. If he refuses to leave, however, that would certainly spark a constitutional crisis."
https://fivethirtyeight.com/features/constitutional-crisis/