Mr Dionne neglects the obvious.

Corbyn showed up for nationally televised debates.  May didn't.

Corbyn crafted an appealing manifesto: "For the many, not the few" in which Labour promised free education and numerous other free benefits while increasing taxes on the rich.  May crafted the worst manifesto in electoral history with her: "Dementia tax" which many feared would cost them their homes.

Corbyn said that he would increase police staffing after 3  bloody Islamic terrorist attacks in 3 months.  May was stuck with her record of cutting 20K police, a decision which may have aided the Islamic terrorists.

Corbyn advocated a "soft" Brexit approach which would keep many links with the EU and would not impose immigration controls.  May could not clearly articulate what she really was going to push for in Brexit.

Even so, the Tories still won the election because the voters did not want Corbyn, a pro-terrorist, Marxist, anti-democratic, anti-U.S.,  socialist with a bad education.