It's actually a pretty good question.
As the Professor pointed out, it was put in place 235 years ago, but a bunch of guys with good intentions but very little practical experience (nobody had any) in setting up a government "of, by and for the people".
The six year, overlapping terms guarantee some continuity, some experience in place.
While it's possible for some sort of 'populist revolt' to peacefully take over congress in one election (not really going to happen, but theoretically possible), it would take THREE major biennial elections to overturn the Senate.
Also, the two houses (and the executive branch) represented 3 different interests.
The House represents 'the people'. Originally direct elections, representation based on population.
The Senate represents 'the states'. Originally elected by state legislature. Each state has equal representation.
The President represents 'the country'. Indirectly elected by the people, then the electoral college. One person. While he (or potentially she) has quite a lot to do domestically, one of the big jobs is to be 'the face' of the country internationally (although the Senate has to ratify any treaties with other countries).
All of it is part of the 'checks and balances' the founders tried to put in place.
They really wanted to keep one person from taking over.
It worked imperfectly, but pretty well, until the Rs decided to cheat.