Like the multiple pronunciations of "ough" or different spellings for the same sounds in English I've read come from mixing different dialects into one language. Whereas with French, they imposed on centralized set of rules. Or in Spanish, there are multiple languages/dialects in Spain (though I think at least Franco did try to impose Castellano for all). And other countries have their own histories of language homo/heterogeneity routes taken.
What made English turn out the way it did, as opposed to others?
In other words, did England ever try to impose one set of rules on how to say written letter combinations (e.g. 'ough'), like other languages have done, one way or another?