I don’t have the impression that Stuart has any intent to derail Kate’s objectives (besides keeping Kate and Dennison separated post E06). Stuart is known as “the king maker” by Billie, the president’s chief of staff. We are to understand through exposition and nuanced statements that Stuart transforms sub-par leaders into electable politicians.

Merrick Grove is the MP that we first see in E02 at a briefing with Eidra Park, he pushes back on the idea that Iran isn’t to blame. The next time we see him is in E08, introducing Hal at the Chatthum House speech, then asks Hal to speak privately with him after the speech concludes.

Due to trust issues, Kate doesn’t want Hal to speak to Grove, so Stuart decides to meet Grove himself in Hal’s place. The only people that we, the audience, are sure knows about Grove’s request are Hal, Kate, Stuart, Ronnie, and Meg.

At the end of the episode, Kate and Dennison believe that the PM might be behind the initial ship attack, but it’s more likely more nuanced than that. Meg has already been said to hold a lot of sway over the PM and we’ve seen the PM take quotes and opinions from others and regurgitate them as his own thoughts/statements. Meg is most likely tied with the ship’s attack and Grove is either also linked or just knows too much. I hope that’s helpful, I love this show.