"lacked an understanding" is a perfectly fine and usable phrase in written English.
You can use this phrase when you want to indicate that someone did not have the necessary knowledge or comprehension of a given topic. For example: "The student's poor grade on the exam was a result of his lack of an understanding of the subject matter."
They had faith in markets, but lacked an understanding of the limitations of markets and what was required to make them work.
The Marshal assumed his presidential duties somewhat reluctantly, for he disliked publicity and lacked an understanding of the complex political issues of his day.
McBride, who resigned in 2009 over a plot to smear his opponents, said the Labour leader's closest advisers lacked an understanding of what was required to win and would rather be attending a symposium by the French economist Thomas Piketty.
As Miliband predicted he would "defy the odds" to triumph next year, McBride said the Labour leader's closest advisers lacked an understanding of what was required to win and would rather be attending a Thomas Piketty symposium instead.
Despite abundant evidence – a bloody glove, blood drops, hairs, carpet fibres – the prosecution faced a major hurdle in convincing the jury to convict him, in part because jurors lacked an understanding of forensic science.
For much of the 20th century, the contemplative guqin — the favored instrument of Confucius — has lacked an understanding audience and been eclipsed by showier musical instruments, including Western imports like piano and violin.
Do councils lack an understanding of the PRS?
He lacks an understanding of the "intellectual excellence" the position of a Supreme Court justice requires.
He takes no credit, and we lack an understanding of his motive.
He lacks an understanding of history and our future with regard to energy, education and foreign policy.
The U-turn comes a week after the shadow chancellor, Ed Balls, taunted Osborne for lacking an understanding of "basic economics" when the scheme was launched earlier this year.
