It is somewhat strange that President Nixon was so concerned about covering up for the Watergate burglars. After all, he did not (so far as we know) personally have any knowledge of their actions and he did not order them to be done. Therefore, it would seem that he would not have needed to cover up those actions. Instead, he was already participating in covering them up only a few days after the break-in.
The best explanation for this is that Nixon was a very defensive person and he worried that the scandal might harm him politically. People in power often get this way. They try to control everything that has to do with their image even if a more objective observer would be able to see that the cover up would have a worse effect than admitting the actual crime would have.
If Nixon had simply allowed the burglars and the officials who controlled them to take the fall for their actions, he would likely have been reelected and served out his term. Instead, he felt that the burglaries would somehow be used against him and he did not want to let that happen. Therefore, he participated in covering up the incident.