brightness keeps going up on Ipad pro

You appear to have tried the majority of obvious steps - bar one. Try a forced restart - as this will often clear an isolated software issue:

Force restart iPad (models with Face ID or with Touch ID in the top button)

If your iPad doesn’t have the Home button, do the following:

1. Press and quickly release the volume button nearest to the top button.
2. Press and quickly release the volume button farthest from the top button.
3. Press and hold the top button.
4. When the Apple logo appears, release the top button.

Force restart iPad (models with the Home button)

Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.

If the problem persists after performing the restart, it may be necessary to reset your iPad settings. While this reset will not cause any loss of data, as a precaution, it is always wise to ensure that you have a current iCloud or iTunes backup before performing the reset:

How to back up your iPhone, iPad, and iPod touch - Apple Support

When you are happy to proceed, you can perform the reset from iPad settings:

Settings > General > Transfer or Reset iPad > Reset > Reset All Settings

If the problem still doesn’t clear, you would be best advised to seek assistance directly from Apple Support. You can contact the Support Team using the Support link at top-right or bottom-left of this page. Alternatively and perhaps easier, you can initiate and manage your support cases using the excellent Apple Support App. If not already installed on your iPad, the App can be downloaded from the App Store:

https://apps.apple.com/app/apple-support/id1130498044

Everyone is making the same mistake, myself included, because of bad UI.

A user naturally intuits that the switch for auto-brightness is in: Settings->Display & Brightness (because that is where it should be). It isn’t.

To make matters worse, there *is* a switch right where the user expects, called Automatic. That is a switch for the iPad to automatically switch from light to dark modes, in the UI, and the brightness slider is below.

The switch for Auto Brightness is, confoundingly, instead under: Accessibility->Display & Text Size->Auto-Brightness is at the very bottom.

You’re very welcome. I’m delighted that the problem was easily resolved.