One of my content website has search impressions dropped from 2k to 20. Why is that?

Has there been any recent Google update? The drop from 2k search impressions to even less than 30 per day is drastic. Why has this happened? If low-quality content might be the reason then I have another blog with very thin content but there's no change there at all. Can someone please help me identify the reasons for this plunge? How can I investigate the real reason? I don't see any page getting de-indexed in the GSC as well. Is this normal and temporary? Your suggestions are highly appreciated.