Fullcalendar / eventdidmount - issue with "more link"

Question

i would like to understand why "+x more" link in the bottom of day cell doesn't work when i add info.event.setProp('display','block'); in eventDidMount ?

Codepen.io example

Many thanks in advance !

    eventDidMount: function(info) {
      var tooltip = new Tooltip(info.el, {
        title: info.event.extendedProps.description,
        placement: 'top',
        trigger: 'hover',
        container: 'body'
      });
      info.event.setProp('display','block');
    },