Why does vice president take oath first?

Its simple Showbiz. Just like the Oscars (tm)

You announce the runners up, then the winner and then do a flurry of congratulations and speeches and ceremonial stuff.

Wrong^^^

actually the reason is that if something were to happen to the president the vice president would be in position to take over. No that's not it. It really doesn't matter whether they're sworn in or not, once they're selected by the electoral college, THEY'RE IN. The VP is sworn in before the Prez because on tradition and want for "importance" of the VP position. The VP is President of the senate, and the VP used to be sworn in in the senate. This was done before the last day that the senate met, with both the incoming and outgoing senators present. This just happened to be before MARCH, which is when the Pres and VP took office in the "Old" days. This has changed to January now. Well, a few decades they decided to do it in conjunction with the Presidential Inaguration and just did it first out of tradition. It has nothing to do with succession, that's already spelled out very clearly.