While there is a chance that the over-ambition is theirs, it very well could be yours. When one party completely succeeds in taking over a project, there is an imbalance of knowledge or personality somewhere. If it's knowledge, then you need to do some research so you can intelligently and calmly argue with the DP. If you feel that their judgements are off, you had better know exactly WHY they are off. And if it's strength of personality, then stand up for yourself and, again, calmly debate the DP instead of coming off as an egoist.
