There are a couple of bits that you've got mixed up:
First, as Stephie wrote, holding someone or something accountable means to consider them liable (usually for the actions that they had control over.)
From the Free Dictionary's definition of the idiom:
hold someone accountable (for something): to consider someone responsible for something; to blame something on someone.
Here we're talking about a corporate entity that has done something wrong, and we're considering who should take the blame for that behavior.
Secondly, management refers to the people in charge at an organization. From Merriam-Webster:
management(n) 3 : the collective body of those who manage or direct an enterprise
Finally, the sentence must be read considering the context in which it was written. The sentence seems to be referring either to corruption (a business misusing or stealing money from the government) or perhaps to the 2007-2008 financial crisis (many businesses were responsible for enormous damage to the world economy with little or no consequences to the individuals in charge.)
So, with all of that in mind:
The government must hold managements accountable for wasting the people’s money.
means
The government must consider those people who are in charge of companies that have wasted the people's money to be responsible for their companies' actions {and be punished accordingly.}