Well, that's because the airplane had to have high ground-clearance because of the pod. Since the pod also made it impossible for the long wheels to fold inward without a complex telescoping landing-gear strut: They ultimately decided to fold it backwards.
Since low-drag was based on the wings being streamlined and thin, the fairing the gears fit into would have to be small, and since bombers normally have four large wheels on a strut, that wouldn't work. So they used a whole bunch of little wheels that made a suitably flat arrangement that distributed the plane's weight. This folded backwards into a fairing which was blended into the rest of the wing.
Amazingly, the landing-gear, despite it's complexity, seemed to have little major problems. The XB-70 ran into loads of problems.