Roberts wanted that fact that court's decisions aligned with GOP policies to appear to be happenstance; just a quirky coincidence.
To keep up the farce, Roberts wanted to slow the rate of change, which is why he occasionally gave Dems some wins, like the upholding the ACA.
Alito basically said f*** that noise, I'm too old, and there are 6 of us, so I don't care what you think, we are going to put as many policies in as we can, before someone stops us.
Roberts is basically humiliated by all this, because the worst possible outcome for him - and the court - to be seen as a political body, which is now undeniable.