Why did plants have to be on earth before animals?

Plantae are autotrophic (meaning they can produce their own food) and are always the producers and comprise the first trophic level - whereas most other forms of life including Animalia are heterotrophic and depend on producers (Autotrophs such as plants) to metabolise and store energy from processes like photosynthesis for their own food. This means that animals couldn't live without plants to provide their food and that plants needed to be around before animals - mostly as animals need plants but not the other way around.