I'm not a fan of the splitting of Kamloops, either; is it really so hard to put Kamloops in one district with the rural areas around it split up instead?
Kamloops has 80% of the population of the two districts.
Okay, so put the center of Kamloops in one district and the outer areas with the rural areas in another.
It looks like Kamloops has two centers. Kamloops is at the junction of the North and South Thompson Rivers, with the Thompson River flowing to the west, the South Thompson flowing from the east, and the North Thompson entering at a right angle from the North.
North Kamloops is on the west bank of the North Thompson. There is a bridge over the Thompson to the south, but it is rather on the western edge of the built-up area of Kamloops which is actually a bit further east along the South Thompson. So you could end up with two central areas that aren't adjacent to one another in one district. And then another district with less developed areas and then more rural areas attached.
In the case of Prince George they were able include the densely populated center in a single district.
If the city is naturally divided, it only makes sense to use this natural division as a border.