No. Don't get yourself confused by the 2008 map, take a look at 1996 or 2000 instead. Noone was going to consider Boise the Dems' strongest area in 2000.
Boise also happens to be slap bang in the middle of the state and it's difficult to get from the one end to the other except via Boise - there isn't actually a sensible alternative to splitting it (though the exact split might have been done better.)
Not that I know much of the state legislature at the time, but I got the idea from that Boise has a majority of Idaho Democrats in the legislature. There are 35 legislative seats (State House uses the same districts, just elects two reps instead of one Senator), and there are 7 Democrats. Four are from Boise, the remaining ones are from Blaine County, Pocatello and I think the area around Moscow.
If redistricting is non-partisan in Idaho...odd, but I guess shoots down my theory of all of Boise being removed from ID-01 in 2012.
