Complex sentence: He became widely popular in his lifetime, and remained so after his premature death at the age of 39 in New York City, but had by then acquired a reputation, which he encouraged, as a "roistering, drunken and doomed poet".
Split into simpler sentences: He became widely popular in his lifetime and remained so after his premature death at the age of 39 in New York City. By then, he had acquired a reputation, which he encouraged, as a "roistering, drunken and doomed poet".