Geographical placement of teams in the NCAA pretty much ended in 1979 once the tournament was seeded. It became more important then for the tournament to have parity throughout the regions rather than having teams make short trips.
One factor that allowed this to happen was money. Until the 1980s, schools could actually host first and second round games. Now a team cannot play on its home court except for the Final Four and since those are all played in big domes now, nobody would be affected.
However, prior to the 1970s, the NCAA tournament wasn’t nearly as much of a big deal as it was now. Few games prior to the Final Four were on national TV. The Final Four would be held in places like Cole Field House instead of the Metrodome. Teams were kept in their own region to save on travel costs and boost attendance. In the 1970s, nobody would think that anyone in Memphis would pay good money to go see Cal play Fresno State.
However, this year, those two teams are playing out there in the South region.
UCLA benefitted greatly from the geographical placement of teams during the Wooden era. The rest of the teams in the West Region during the 1960s were not particularly strong. Not until Jerry Tarkanian built up Long Beach State was there any serious competition for UCLA.
That’s not to say that those UCLA teams were still not head and shoulders above all the rest, but they usually weren’t tested until the Final Four, if at all.