system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is a conductor necessary for an orchestra?

And is he anything more than a glorified metronome? I mean, even the dynamics are written down on the sheet music...

Edit: I guess I really have two questions: 

1. What exactly does a conductor do?
2. Could an orchestra, er, "conduct" itself ok without the conductor?
gpt
99% of what the conductor does happens outside of the performance.

He selects the music, arranges the music, organizes rehearsal, manages the musicians and basically does everything required to put on the performance.

The part where he waves his arms around, that's just the culmination of many months of works.  That is important too, he set the tempo and cues the musicians, but compared to the rest of what goes into preparation, that part is minor.  If the conductor was ill, an reasonably skilled assistant who has been involved in the process could take over baton duties without losing much.