Trump may not want war but everyone around him does take Mike Pompeo for example he has been calling for a full scale war and regime change for years even more for Bolton's crew left in the white house. Trump may not want war but he keep surrounding himself with neo con war hawks, the same can be said for Iran. When the US walked away from the nuclear deal all the moderates got pie on their face because the extremists told them that the US could not be trusted.
So we are in a situation that while there are leading people not wanting war they are outnumbered by extremists salivating at the prospect. As for the demonstration the US didn't do anything at the peak of demonstrations under Trump where the Iranian government killed hundreds of people doubt he will step in now. Also while those protestors maybe against the government they have no love for Donald (I love committing war crimes) Trump either.
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The secretary of defense owns stock in defense contractors he will make millions off a war with Iran.