We computationally investigated the role of the omicron RBD mutations on its structure and interactions with the surrounding domains in the spike trimer as well as with ACE2. Our results suggest that, compared to WT and delta, the mutations in the omicron RBD facilitate a more efficient RBD "down" to "up" conformation as well as ACE2 attachment. These effects, combined with antibody evasion, may have contributed to its dominance over delta.