Yes, there were some of the usual uniquely Trumpian flourishes—the factual hyperbole, the sarcastic mockery of the opposition, the dubious stories of people being moved to tears in his presence. But the relative lack of interruptions and constant cross-talk this time around exposed the familiarity of the actual substantive terrain over which the candidates fought.
Joe Biden acted very much like a typical Democrat. He came to the debate armed with summaries of specific policy proposals to address specific social problems, along with associated facts and figures: a public option for health care, a climate change bill, an immigration reform initiative. He pledged to protect the interests of specific groups within the Democratic coalition, such as labor unions, African-Americans, and the "middle class" more generally.
Trump, for his part, exercised the usual Republican counterstrategy against such an approach. He conceded ground on many of the specific policies, and even tried to outflank Biden at times (as on criminal justice). At times, his attacks did not target the content of Biden's proposals at all, but instead cited Biden's lack of success at achieving them while he was in office.
But Trump also described Biden's agenda in a more general sense as ideologically radical, associating Biden with left-wing figures like Bernie Sanders and Alexandria Ocasio-Cortez. He warned that Biden's election would threaten the future of America as we know it. And he repeatedly cited various stories and claims that circulate in the conservative media but are less well-known outside its regular consumer base.
That Joe Biden is a walking personification of his party is hardly news. But beneath the idiosyncratic exterior, Donald Trump has himself become an increasingly orthodox Republican over the course of his time in politics. In both his rhetoric and his substantive positions, Trump hews more closely to party doctrine today than he did in 2016, and his instincts in the heat of the debate reflect this evolution.
Many media commentators opined afterwards that the debate didn't break any new ground. That's a reasonable characterization. But one big reason why is that each candidate adopted the traditional playbook of his own partisan team, playing to its perennial strengths and defending against its weaknesses. In a year stuffed with unprecedented developments, it was a rare moment of political conventionality.