It's k____ to all that bill gates is a famouse person all over the world

be known to all
是个词组，表示众所周知的意思

It's known to all that Bill Gates is a famous person all over the world.

众所周知比尔盖茨是个家喻户晓的人物

known
It's known to all that bill gates is a famouse person all over the world
众所周知,比尔盖茨是世界上有名的人物

known
It's known that是一个固定的用法，作文中经常出现的

known

比尔盖茨是世界上很著名的人是众所周之的。

known

It's known to all 意思是总所周知的是... it 是形式主语, that引导的是真正的主语.