It's great that the Washington Post has so many reporters with mind reading abilities. As a result, we know that Trump is "convinced that his attendance at the G–7 summit is essential."
Good to know that Trump is convinced of this fact. Otherwise, we might just think it would be too politically embarrassing for him not to show up just after a statement from G–7 (minus the US) finance ministers condemned his trade policy.
If news outlets like the Post didn't have reporters with mind reading abilities, the rest of us would just know what politicians say and do. We wouldn't be able to learn what they actually think.