Today, MicroStrategy announces proposed private offering of $400 Million of senior secured notes to acquire additional bitcoin . And it looks like, Michael Saylor is on the mission to overtake block(dot)one in terms of hodling bitcoin and take bitcoin to the moon. Lets see who will win the race for being on the position of top institutional investor. 
Reminder
Indeed, there are more companies outside USA which already bought bitcoin and didn't make it public yet. So actual hodlings of bitcoin by institutional investors/companies are still unkown and we can just get a rough idea of the hodlings through those websites. - They are tips of iceberg. There are probably more companies have investments into Bitcoin
- They just have yet publicly announced their investments