There wasn't a single broker. Each of these banks (8 in total I think?) all let Archgeos separately secure this levered up high-risk position. The margin call

There wasn't a single broker. Each of these banks (8 in total I think?) all let Archgeos separately secure this levered up high-risk position. The margin call references are quite apt. I believe it was a literal margin call. Goldman and Morgan Stanley forced Archgeos to square up their position, which forced Archgeos to liquidate their stock, which drove down the stock, which left Credit Suisse (who had been hoping for the banks to slowly unwind the position) in a terrible spot.