What was primarily responsible for the development of life outside oceans?

The primary factor responsible for the development of life outside oceans was the evolution of plants that could tolerate drier environments. During the Silurian period (approximately 444 to 416 million years ago), certain plant groups such as mosses and liverworts started adapting to life on land with the ability to grow on rocks and moist soils near the shorelines. These pioneers of terrestrial life developed specialized structures like vascular tissues to transport water and nutrients, as well as waxy cuticles to prevent water loss in drier conditions. The spread of such early plant life created favorable environments for other organisms such as insects and amphibians to colonize land over time. This subsequent terrestrialization set the stage for the diversification and evolution of a vast array of organisms outside the aquatic realm.