It’s a sobering detail of our situation. In 2020, Trump really did receive more votes than any candidate in any previous election. That means a ton of people showed up to vote for him in 2020 that hadn’t in 2016.
He frames it weird (and it sounded weird when he said it) because otherwise it raises the obvious point that Biden also achieved that same record, plus an extra 7 million votes.
This is known as the “Dead Sea Effect”