There is kind of a way to do this. A couple of things to note:
1. The feed itself may not contain all past events. Generally the calendar server will drop old events off the feed at a certain point to keep it from getting ridiculously large.
2. The plugin doesn’t have a way to automatically show all past events that are in the feed, nor to have a rolling update (e.g. “all events from the past 3 months”).
What you can do is set an arbitrary start date for the feed, e.g.:
startdate="20190101"
That would show all events starting from January 1 of this year. You can edit that startdate value in the future as needed.