What do geckos, mussels, and spiders have in common? They all have their Mercedes in the Driveway™, in their case, exquisitely designed adhesives that outperform those designed by mere humans.
What has caused this phenomenon in nature? Nature itself. Nature is its own cause.
"Nature has evolved a myriad of well-designed adhesives that assist in locomotion, self-defence and prey capture. Geckos use micron-sized hairs... Mussels secrete specialized proteins... Modern orb-weaving spiders use micron-sized glue droplets..."
"Nature has evolved". The language suggests an agent, Nature, acting on objects, i.e., life-forms. In fact, there is no real distinction between Nature and life-forms -- life forms are part of Nature itself. You might just as well say, "Evolution has evolved" or "Nature has natured".
Elsewhere, the objects of the purported agency of Nature are themselves the purported agent: "modern orb-weaving spiders have evolved well-designed adhesives...".
In other articles, "evolution" is the agent, as in, "Evolution has produced...".
What is not in dispute is that we can look upon the results achieved and conclude that they are good. You might even say, "very good", for they are "well-designed".