> Didn't Trump nominate the supreme court justice? And isn't the nomination confirmed by congress? What about the constant conservative vs democrat number battle in the supreme court?

There's deliberately limited legal ability for the legislature or the executive to influence or impose penalties on a serving judge, and the rule of law means that the president can't apply extra-legal pressure either. A judge could removed from office for really extreme or criminal behaviour, but that's considered extraordinary.

Day-to-day, judges can rule against governments and politicians without any fear of reprisals. The selection process just weeds out people who are likely to frequently make such rulings.