(1) The media's attention is going to turn to the attack in London, which means less focus on the unpleasant (for him) testimony that came out of the House Intelligence Committee's hearing earlier this week. You know ... about no evidence of wiretapping, and all those ongoing investigations into the campaign and Russia and collusion ... and the fact that someone has actually used the "T" word (and "T" stands for treason, not Trump).
(2) He can take the attack and run with it, using it to "prove" that the courts are wrong to block his travel ban and MUST STOP DOING SO IMMEDIATELY!
(3) He might even be able to whip the House Republicans into a patriotic frenzy and get them to pass that healthcare bill that neither he nor House Speaker Paul Ryan wants named for them (and doesn't that tell you what proud parents they must be). The vote in the House is scheduled for tomorrow, in case you'd forgotten.
(4) Maybe people will forget that Ivanka and Jared have been publicly referred to as "the de facto First Couple", when that description is supposed to apply to The Donald and Melania. (And speaking of Melania, quick, Fou and Tavi and Jen and anyone else who knows a little about recent French politics, what other First Lady in Absentia is she starting to resemble?)
Now, a really cynical person (which of course I'm not) might look at the convenient timing of what happened on Westminster Bridge and outside Parliament today and ... wonder.