Congress cuts funding for a program that (at least on the SpaceX side) is well advanced in producing a man-rated booster and capsule to replace the Russian rides to the ISS and yet they INCREASE funding for a program that has yet to even produce a full-size prototype, doesn't have a proper mission yet, just some thought bubbles AND is costing far more than it would cost if you just said "this is what we want the rocket to do, who can build it for us"
I think there are 2 things going on here.
First is that there is an election comming up and the votes of a bunch of ATK workers in Utah who have been promised jobs in the SLS program to replace the jobs they had in the shuttle program are somehow important enough to matter (which is a reflection on just how broken the US political system is). Hence the increase in funding for SLS to get it to the "actually building stuff" phase much faster. (and to assure the workers in question that their jobs are safe)
And second is that SpaceX has the lead in producing a crew rated capsule right now (their crew capsule and rocket are a modified version of the capsule and rocket they are launching to the ISS already whereas Boeing has to develop a capsule from scratch) so the cut in funding and the delay is a chance to give Boeing time to catch up (since Boeing is too politically and economically important to allow SpaceX to win this race on its own)