幸い・幸いなことに

幸いなことに is used to talk about something favorable or fortunate that happened, often followed by a clause that describes the result or situation. It has a formal nuance and is common in writing or careful speech. In casual speech, people might simply say うまくいって幸いだった or just 幸いだ, but 幸いなことに carries a sense of relief and foregrounds the favorable turn of events.