His position (which is explained on his webpage: http://www-cs-faculty.stanford.edu/~uno/email.html) is a little more nuanced. Relevant section:

> Email is a wonderful thing for people whose role in life is to be on top of things. But not for me; my role is to be on the bottom of things. What I do takes long hours of studying and uninterruptible concentration.

I think he would agree that a President's role is to be 'on top of things'.

I think it would be reasonable to conclude that "don't believe in email because I can't be bothered to do computer stuff" is different from "don't believe in email because I understand all relevant technology from top to bottom and have made an informed choice."

It's not clear that Knuth would be a particularly knowledgeable leader on these issues either, whatever his other strengths.

That's a fair argument. However, the reason behind Knuth's conclusions are inevitably different than Trump's. So, I think it shouldn't be compared.