If the world came about after a "Big Bang", as some scientists say, how could the detail seen in nature be explained?

Answer 1

Earth was not formed in the "big bang" ... ~ 14 billion years ago

our solar system is part of a later generation of stars ... ~ 4 billion years ago
... the Sun has more than just hydrogen and helium

the heavier elements (that make up the Earth)
... were forged in supernova explosions of earlier stars

as to "the detail seen in nature"...it is the result of time and evolution