It looks different if you only consider a smaller area
The pressure for the Berkeley-Oakland loop route must come from trying to get a shorter path for longer-distance travel. If you consider only a smaller area, you get something that looks more like Oakland's branchy street system.
In this view, Telegraph is the street most neglected by existing rapid transit infrastructure.
Perhaps worth comparing to a long ago promotional brochure about the centrality of downtown Oakland.
(21167 trips routed through 1000 geotags. Data from the Twitter streaming API. Base map from OpenStreetMap, CC-BY-SA.)