From: American Banker
First, with a turnover in political party, the Trump administration will enter a White House entirely devoid of resources or personnel. Even the software is likely to be removed from the computers. With transition teams working on issues and appointees, the vetting process is gradual and uneven. The initial focus has been on filling Cabinet-level positions. Second- and third-level administrative positions will likely go unfilled until key Cabinet officials are in place, which could take until at least the spring of 2017.
Second, major change requires either legislation or changes in key administration leaders. Though Republicans retained control of both the House and the Senate, Trump has done nothing to establish allies in either body, so he is unlikely to ask congressional leaders to develop policy agendas. That means he will need knowledgeable people both in the White House and in the various departments. These appointments take time and often require Senate confirmation.