Possible interpretations of 'Dont screw this up';

This was the first time TDO told Redcloak to keep fighting for the gates. He might have been tempted to settle for Gobbotopia, destroy Xykon and put his feet up. His God didn't want him accepting a silver medal when gold was still an option.

TDO knew Redcloak would be a *terrible* leader, whose hatred and neuroses would pit Gobbotopia against any nearby human territory and fall victim to the same problems Tarquin faced on the West Continent. While Redcloak was an effective war leader, he wasn't the right goblin to rule peacefully. Getting Redcloak out of Gobbotopia and back on the campaign was the best chance of Gobbotopia surviving indefinitely.

It's possible both are true.