One of the main roles of police during the 19th century was "strike-breaking." Why did the police engage in these actions and who benefitted from these actions?

The police engaged in strike-breaking because in the 19th century, labor unions were starting to emerge, and they had a low reputation among the political ruling class and the economic elite. This is because labor unions represented and obstacle to their profits.

Those who benefited were mainly the economic elite who owned the enterprises. These owners did not want to meet the demands of the labor unions, like an 8 hour work-day, simply because these demands represented a reduction in profits.