This Bitcoin sell-off is historic in the magnitude of losses realised by short term holders.
STH-SOPR has only dipped this low on three occasions since 2015: - Feb 2018 start of bear market - Nov 2018 bear capitulation - Mar 2020 COVID sell-off
According to Chainalysis, institutions were not significant sellers. Bitcoin inflows into exchanges were relatively low compared to past sell-offs, at 412k bitcoin in the last three days, compared to 412k on the 13 March 2020 alone — link