Twenty years ago African government committed to eradicate polio.
句子的谓语是： commit to do sth. 承诺做某事

我把commit 表示“承诺”的用法，列为三组：

A 组：
He committed himself to supporting his brother's children.
He committed himself to support his brother's children. （美国英语）

B 组：

He was committed to supporting his brother's children.
He was committed to support his brother's children.

（去掉反身代词，变为被动式，但意思并无被动，同A组）

C 组：

为求简练，省掉A 组的himself，或者人们觉得， B 组用was 啰嗦，直接也省掉。得到：
He committed to supporting his brother's children.
He committed to support his brother's children.

最后一句，commit 的用法跟网友的句子一样。

新闻语言、网络语言、包括口语在内的非正式语言，无不都在简化表达方式。
当今社会是信息时代，时间是最宝贵的。因之，语言交际趋向简洁明了。“简练”是语言的精髓。现如今，新闻语言和网络语言，占据着人类交际语言的半壁江山。由各种多媒体承载的语言素材，纷沓而至，应接不暇。语法研究也要与时俱进，不要一味地从故纸堆里，包括数十年前出版的英语语法书、英文词典、英文报刊，以及古典文学作品中，寻找一成不变的理论根据，否则就会落伍的。