I'm not sure if there is an easy way to do this when looking back at past interesting moments, but you could set up a smart campaign to track this going forward. One option is to create a custom scoring field called "Interesting Moment Score".
You could then set up a smart campaign with the trigger "Has Interesting Moment: Type is any" and a flow action of "Change Score: Score name is 'Interesting Moment Score'" = +1.
Your interesting moment score should then reflect the number of times an interesting moment has occurred for each lead. In the future you could take the average Interesting Moment Score for all MQLs to get an average count of how many interesting moments happen between acquisition to MQL.