While the theory of plate tectonics is a complex one that developed over time, the scientist most commonly associated with its development is Alfred Wegener.

Here's why:

* Continental Drift: Wegener is best known for his theory of continental drift, proposed in 1912. He observed the fit of the continents, the matching geological formations across continents, and fossil evidence. However, he lacked a mechanism for how continents moved, which is why his ideas were initially rejected.

* Seafloor Spreading: Later, in the 1960s, scientists like Harry Hess and Robert Dietz proposed the theory of seafloor spreading, which explained how new oceanic crust was created at mid-ocean ridges and moved away.

* Plate Tectonics: Combining Wegener's ideas of continental drift with the theory of seafloor spreading led to the development of the theory of plate tectonics, which describes the Earth's lithosphere as broken into plates that move and interact.

So, while Wegener's initial theory was incomplete, it provided the foundational groundwork for the later development of plate tectonics.