Complex sentence: Kayfabe was long held as a closely guarded secret within the professional wrestling industry; however, with the advent of the Internet, it has evolved into an open secret in the industry that is generally only adhered to while performing.
Split into simpler sentences: Kayfabe was long held as a closely guarded secret within the professional wrestling industry. However, with the advent of the Internet, it has evolved into an open secret in the industry that is generally only adhered to while performing.