Too much hysteria about terrorism. We've always had theft, kidnapping, arson and murder, whether it's done for money or for politics, who cares.
The soldiers would not be wearing their uniform because someone ordered them not to. The military is the same as any other public service or non-profit organisation, they worry a lot about image. For example, when I was in we weren't allowed to go to civilian pubs in uniform. Civvies resent soldiers in towns with a lot of soldiers, there are confrontations from time to time, add in alcohol and it's worse. And appearing in uniform makes the confrontatins more likely. Remember soldiers are mostly 18-25yo males, even if they haven't been deployed they've done some tough things and been through some sht together, so they tend to be a bit cocky and loud and it's easy to start a fight with them.
Soldiers getting into drunken brawls while in uniform, images appearing in newspapers or telly (or nowadays, social media) - the brass don't want that. Soldiers stick together, so if some civvies pick a fight with them, you end up with a picture of six soldiers kicking some guy while he's down on the ground. Or if it's an individual soldier who walks past some bunch of radicals (moslems, socialists, same sht) and gets beaten up, and then images of that appear across the country, imagine the fcking drama.
Whereas if they're in civvy gear, confrontations are less likely, and if they do happen, less likely the story goes nuts across the media. Army doesn't want any drama, it's why they kept journalists out of Afghanistan.