Whilst they may often be among the most technically proficient in a group, Alpha Geeks often exhibit other traits that push them to the fore in any group:
Volume. The Alpha Geeks in my department acheive superiority by raising their voice and literally shouting down those who oppose their ideas.
Intimidation The cause of an Alpha Geek's volume may be the wish to force their view by intimidating those opposed to them.
Selfishness An Alpha Geek may choose to simply ignore the views or wishes of those He/She sees as being less qualified than them.
It is for these reasons that Alpha Geeks Make Bad Managers, but it is also for these reasons that Alpha Geeks are made managers by reason of their seniority.