Archegos was at 15% equity / gross positions and had stakes as large as 25% in their investees. Their positions were enormous, concentrated and not reported on a 13F because Archegos was a set up as a family office. All according to WSJ. What they were thinking, who knows, but I bet it involves lots of talk about beta, other greek letters and VaR.

https://www.wsj.com/articles/inside-archegoss-epic-meltdown-...