stumble into something
phrasal verb with stumble verb uk/ˈstʌm.bəl/ us/ˈstʌm.bəl/
偶然开始做（某事）
to start doing something by chance, without having intended to do it
He had stumbled into teaching English after he finished college. 大学毕业后，因为一个偶然的机会他开始教英语。