Calendar app not showing events — only as weird thin lines

The calendar app on my iMac is showing events only as these thin lines, without an option to expand them at all. I tried playing around with preferences and different settings, and...nothing. I have the same calendar on my iPhone, and everything shows up totally fine and normal there. Has anyone seen this before?

Each of those thing lines are normal events — things like meetings, Zooms, etc. Any ideas?