Based on race only. Yes, or more accurately, based on ethnicity only, since the Hispanic minority district was the only one rejected.
Exactly. The SCOTUS had endorsed an affirmative action rule for gerrymandering. Its not exactly a gift horse for the Left; quite the contrary - it locks them into representing fewer voters than they otherwise could win in a district that was NOT racially gerrymandered. The SCOTUS put the Democrats in a political ghetto in Texas with today's decision.
(Denny Crane: "Every one should carry a gun strapped to their waist. We need more - not less guns.")