He surely went off the deep end when he bought that restaurant.

他买下那家饭店的确太贸然行事了。

《新英汉大辞典》

And then he went off the deep end.

但是他到了另一个极端。

youdao

Tom went off the deep end when he heard the news.

汤姆听到这消息时勃然大怒。

youdao

The news, care of From the Jaws of Victory, is that in the face of all these victories, Chavez became a megalomaniac and went off the deep end and his movement perished from the earth.

FORBES: Unions Tend Toward The Weird, As The Life Of Cesar Chavez Showed

Let's face it, some high-income taxpayers went a little crazy in recent years, and some tax advisers went clear off the deep end.

FORBES: The IRS Wants You To Fess Up