This wasn't a 5-4 split, it was 6-3. We have these splits because some judges play partisan politics and there are sometimes genuine disagreement about meanings.
To rule as Scalia would have liked would have made a mockery of the other 2500 pages. You had a single sentence, nay a single word that was incorrect against 2500 pages that said the exact opposite. To take this one word as paramount over the remaining 2500 pages is the real mockery.
This is EXACTLY what Roberts said in the opinion. The one word is an error, and because of that it's clear the meaning is ambiguous when you consider the totality of the law. Because of that ambiguity they then turn to the intent of the law per their own precedent and the intent is clear, particularly in the rest of this rather large law. To take this word as paramount over the remainder of the law would have required them to rewrite entire chapters of the law.
There's nothing partisan about this ruling. If the ACA was going to fall it should have fell with the first ruling. Bringing in a typo from a single sentence to eviscerate a law that spans 2500 pages is insanity and that would have been partisan.