The cause of tectonic-scale extension in eastern Indonesia remains debated. Previous studies have suggested slab rollback as the preferred explanation for this extension. This hypothesis accounts for the unusual topography of Weber Deep and the formation and development of the Banda Detachment. However, our new data provide seismological, topographical, geophysical, and geodetic evidence for extension without invoking rollback of the subducting slab. These results were obtained by analyzing earthquake focal mechanisms, and seismological data, supplemented with published geodetic and geological information. The ~180° bend in the strike of the Sunda Megathrust fault at the Banda Arc, the spoon-shaped geometry of the subducting slab, and widespread tectonic extension collectively suggest that plate interactions are the most plausible explanation. This interpretation is further supported by Moho depth variations, the distribution of seismicity, the type of earthquakes, and the dominant tectonic structures. Our findings offer new insights into the tectonic extension in eastern Indonesia as a direct consequence of interactions between the Australian, Sunda, and Pacific Plates, without requiring slab rollback.