Unlimited time doesn't do the DM any good at all if they are simply not able to predict what the players will pull, wheras a super-intelligent villain (like Thrawn) would be.
I mean, perfect prediction is impossible sure, but perfection isn't required.
Players are usually reactive, as noted by the recent thread claiming that the villains are actually the "main characters" of TTRPG play. Hence, the discerning BBEG seizes the initiative. As Sun Tzu said, "Thus it is that in war the victorious strategist only seeks battle after the victory has been won, whereas he who is destined to defeat first fights and afterwards looks for victory." Or, in the more pithy translation, "Victorious strategists win first, then go to war; defeated strategists go to war, then seek to win."
And, honestly? Players have a tendency to fall into like, three camps. The Total Jerks (murderhobos, inglorious basterds, etc.), the Puckish Rogues (heroes for hire, loyal to a paycheck, etc.), and the Stalwart Heroes (knights in shining armor, capes, etc.) And you can
usually guess at least the general shape of how these characters will behave. The Total Jerks will do whatever gets them power, influence, etc., because they're selfish and ambitious. The Puckish Rogues are usually in things to have a good time and make some money
that they can spend later, so they'll often drift to the side of Good simply because it's there--but there are distinct patterns in their semi-reluctant good-doing. The Stalwart Heroes will do whatever they think the right thing to do is, with conviction and enthusiasm.
All of these can be manipulated, or prepared for, intelligence as cunning or forethought respectively. Both benefit enormously from all the things I mentioned.
And the main place you can't...is creativity, intuition, and flexibility. Which is what I said. The parts of intelligence that require you to personally,
right here and right now, portray great intelligence in short order. That's something very hard to fake.