iMac won't boot after using migration assistant to new mac studio

Did you restart as I instructed you to? Also, did you follow the instructions in Setup Assistant and Migration Assistant or did you try some other method????? It is critical that you answer all questions if you want help here.

Start with this of M1 or M2 Mac...

On your Mac, choose Apple menu  > Shut Down.

Wait for your Mac to shut down completely. A Mac is completely shut down when the screen is black and any lights (including in the Touch Bar) are off.

Press and hold the power button on your Mac until “Loading startup options” appears.

Select a volume.

Press and hold the Shift key, then click Continue in Safe Mode.

The computer restarts automatically. When the login window appears, you should see “Safe Boot” in the menu bar.

Restart normally.

Okay, I would start all over again. Please start the new Mac in the Recovery Partition ( Use macOS Recovery on a Mac with Apple silicon - Apple Support )and erase the SSD and then install Mac OS from the Recovery Partition. Then closely follow the steps in Setup Assistant and Migration Assistant. If you cannot start in the Recovery Partition, please give AppleCare a phone call for assistance.

AppleCare Contact Info

Okay, did you have any third party antivirus, cleaning, optimizing, security, VPN or any other third party "maintenance" type apps installed on the old Mac? If so that is your problem!!!!!!!!!!!!!!!!!!!!!!

Hold down the power button for about 15 seconds.