The impersonal pronoun, “it”, is frequently used as subjects. It is a common phenomenon.
First, it can be served as an antecedent (先行词) to replace the real subject or object.

eg.

It never occurred to me that she was so timid.
我从来也没有想到她胆子这么小。

Furthermore,

It is said that… It is thought that… It is well known that…
“it” is used to take the place of “that” clause.

eg.

It is well known that when fuels such as coal, oil and gas are burned, energy is released.

众所周知,煤、油和天然气之类的燃料燃烧时会释放出能量。
Second, it can be form word (虚义词) to substitute some subjects that mean certain ineffable phenomenon or situation.
eg.
It’s only half an hour’s walk from here to the campus.
从这里到校园只要走半个钟头。

Third, it can be regarded as emphatic word (强调词), which is hard to translate into Chinese.
eg.
It’s here that we first met each other.
我们初次见面就是在这个地方。

P.S.

it occurs(oc-curred)to me that

it dawns (dawned) on me that

it seems(seemed) to me that

it strikes (struck) me that

These sentences are frequently seen in English, yet there are not corresponding expressions in Chinese. Hence, when translating, it is neccessary to show the real subject.

The next morning it struck me that there was no shower in the flat.

第二天早上我突然想起这套公寓没有淋浴设备。
It dawned on me that I had left the oven on.
我突然想起烘箱未曾关掉。
It never occurred to me for a moment that you meant that.
我从没想到你会是这个意思。
An idiot hope struck me that they might think something had insulted me while I was writing the checque the that I had changed my mind.
我突然痴人说梦话似的希望他们会以为我在写支票时有人冒犯了我,因而我才改变了主意。

It seems to me that the time is ripe for the Department of Employment and the Department of Education to get together with the universities and produce a revised educational system which will make a more economic use of the wealth of talent, application and industry currently being wasted on certificates, diplomas and degrees that no one wants to know about.

在我看来,就业部门和教育部门应该同大学携起手来,修正我们的教育制度,使之更为合理地发挥学生的才能、更为充分地利用学生的勤奋和努力,他们的才能、勤奋和努力目前都浪费在无人了解其意义的证书、文凭和学位上。现在这样的时机已经成熟。