The phrase "were of one mind" means to have a shared opinion or agreement. There are several synonyms that can be used in place of this phrase, such as "in agreement," "in unison," "in concordance," "of the same mind," "united in thought," "of one accord," "harmonious," or "consensual." These terms all suggest a cohesive group that has come to a mutual decision or consensus. The use of synonyms such as these can add variety and richness to your writing while still conveying the same meaning. Regardless of which phrase you choose, the focus is on a unity of purpose and agreement within a group.