The phrase "were in cahoots" indicates a partnership or collaboration between two or more parties for a potentially nefarious activity. Antonyms for this phrase could include "were at odds," meaning they were in disagreement or working against each other. Another antonym could be "were independent," indicating that the parties were operating separately and not in collaboration. "Were estranged" could also be an antonym, implying a complete separation between the parties. Lastly, "were impartial" could be an antonym, suggesting that the parties had no bias or preference towards each other and were acting objectively.