You could argue that in early succession areas species may have not been adapted or evolved. In Darwin's theory, life began in a shallow, warm pond. If that is the case, species would then venture deeper when their area they are in is suitable and having success
I believe rottening would be the answer. Rotting, dead plants and animal feaces make great fertilizers.
Being born with the genes, and evolving to reach food easier
Maybe, IDK Tbh XD