This was probably because, among other things, the vast majority of banks and supervisory bodies had treated the Brexit scenario with the seriousness it deserved and had been prepared for that outcome. Another reason for the lack of severe disruption is that banks are now far more resilient than they were in the autumn of 2008.
Basel II, by tying regulatory capital to bank inputs, offers greater transparency about what stands behind the inputs provided by banks and exactly how they are calculated. As I noted earlier, successful institutions understand that calculating internal capital measures is a serious and challenging undertaking, with many moving parts.