B) Trump's gotten Arab nations to sign peace treaties with Israel. The idea that putting the embassy in Jerusalem would promote more perpetual conflict in the Middle East was always a stupid notion, but with hindsight I can't believe you're making that claim. We're closer to peace between Israel and the rest of the Middle East than we have been in decades.
Yes and no.
The USA has real clout, and the Trump administration threw it around heavily this year in an attempt to score some sort of "win" in time for the election. The USA got the latest concession, for instance, by publicly backing Morocco's claims over Western Sahara, which is heavily disputed. The obvious concern here is if that destabilises the thirty-year ceasefire - and if so congratulations, thousands of deaths so Israel can boast another embassy. Then of course remembering the real basis of Arab - Israeli peace is not actually peace, it's attempting to stitch up a coalition to fight another enemy (Iran). This is even without the tricky issue of what all this means for the Palestinians, who are still completely boned, as if their safety, liberty and human development doesn't matter a damn.
So the first and obvious issue is that Arab-Israeli peace involves exchanging conflict for conflict. The bottom line here being that people - particularly the American pro-Israelis and through them Trump, simply could not give the slightest damn about how many people suffer and die just so long as Israel is sorted. In particular, they barely seem to view the Palestinians as human.
The second is that this is low-hanging fruit - in a way, normalisation is making overt what everyone knows has really been going on a long time that Arab nations have been working with Israel to some degree. The third is that this is all paper thin: the minute Trump walks out, a lot of it can be forgotten or undone. This is not a concrete step towards peace, it's a PR blitz based on nothing but the USA's willingness to pay other countries for the benefit of Israel.