Politics. Diefenbaker had a conservative majority. Destroying everything made it much more difficult for a future Liberal government to restart the program.

Why would a future Liberal goverment restart it if the past one wanted to shut it down but didn't have the guts (or at least that's my understanding of the article)?

Ban / "Burn the books" does seem to fall on the 'conservative' side of the spectrum every time I can recall.

That is why Trump supporters are buying Teslas.

They are electric and have no trans.

That's only a funny joke if you dare to tell it right. Transmissions are called trannies.

Killing it was the right call for the wrong reasons. But because it was the wrong reasons, it meant that no attention was paid on investing the tech into a new plane or resources.

Diefenbaker being "suckered" by the Americans is not what really happened (the CBC mini-series on the Arrow has some really cringey scenes about that angle, as well as portraying conservative party ineptitude and American arrogance). The more you read into Diefenbaker, the more he comes across as vain and susceptible to overreacting to slights (perceived or real), in over his head on the international stage, and ignorant of cold war realities (despite it being his government that had Canada form NORAD with the US).

It did set the stage for Canada's mercurial relationship with the United States, as Canada tended to over-react and over-compensate our opinions in both directions since then. This still continues to this day.

Besides security reasons?

Which security reasons does the article state for not keeping at least one prototype (in a museum, without security-ensitive parts) and the blueprints?

As far as I can tell they only kept part of the nose/cockpit.

Honestly asking, I might have missed it.

Interestingly, the nose of the plane was only preserved because someone hid it. It was supposed to be destroyed too.

The article doesn't get into how Soviet spies were uncovered in Canada in the 1950s and 60s. Governments were not being paranoid in the face of those revelations.

Right, the spy threat would be the "security reasons" I guessed at.

But still, wouldn't successful projects which were later decommissioned be more at risk of spies than an unsuccessful project? Yet successful projects do not have their blueprints and airframes routinely destroyed without a trace.

Humiliation ritual.