Learn Turkish: Meğerse şirketin iflas edeceği çok önceden malumdu. - It turns out that it was known long in advance that the company would go bankrupt.

Because the entire clause şirketin iflas edeceği ("that the company would go bankrupt") acts as the subject of the main word malumdu ("was known"). When a factive clause functions as a sentence subject, it takes the possessive suffix (here, the 3rd person singular -i on the future suffix -ecek, softening the k to ğ) but remains in the nominative (zero) case.

Why is the company written in the genitive case (şirketin) instead of just şirket?

In Turkish factive clauses built with -dık or -(y)acak, the subject of that specific embedded clause takes the genitive case. You can think of the literal grammatical structure as "the company's future-going-bankrupt was known".

What nuance does meğerse add to this sentence?

Meğerse (which can also be used as just meğer) means "it turns out that" or "apparently." It is a discourse marker used when a speaker discovers a truth that contradicts what they previously thought or didn't know. It emphasizes the speaker's surprise that the bankruptcy was actually expected all along.

Why does önceden take the ablative (-den) case here?

With time words, the ablative suffix often denotes the continuous starting point of a state, translating to "from" or "since." Çok önceden literally translates to "from much earlier," which gives us the natural English phrasing "long in advance."