Have an idea and I want to share it. Why? Because I don't know how to do it.

I actually did that in a hackathon. Was a real easy setup. Here the video:
https://www.instagram.com/p/BpzaJ30ASvZ/?utm_source=ig_web_button_share_sheet

Here is the code for it (Backend in go, frontend in js with websockets)
https://github.com/simonfrey/crowdlight

And btw. you can completely realize that with a webpage...so no app download included.

Might want to Google the history of https://en.wikipedia.org/wiki/Photosynth - not the same idea but some similar elements

Concerts many times hire a small broadcast crew to either film the concert or just do sidescreen video.
I know this because I have worked those gigs myself. A professional team is overall cheap and good.

What you could do is augment their sources.

There was a beastie boys crowdsourced concert film called, Awesome, I f...in shot that.
Radiohead also did a crowdsourced film

CrowdAlbum seems like it did this, was acquired by Spotify.

Evergig in 2013: https://youtu.be/yQUIccZ5-zc

First of all, this is 100% technically doable.
It's quite easy to test it with a relatively small audience, like 25 people.
You can pre-synchronize them with a camera of one more smartphone

I would say it could be quite nice to watch.

I also totally don't understand how would you make most of the people to install the app.

Hey, I was looking for a similar app that could share and transfer anything from a few months ago and I found a plethora of apps on various websites. However, a lot of them were not very practical, because they would only transfer videos or photos or files. I found an app on this website https://www.apkdojo.com/vmate after some days and it did everything just the way I wanted. I suggest you try to make a similar app to this one if you want to build a practical and usable app.