MacBook Air M1 Choppy & Stuttering with 4k playback

Hi there, I need some help.

I recently bought a MacBook Air M1 with 16GB RAM. I edit a lot of videos in DaVinci Resolve and it's been great i.e. No lag or noticeable performance issues. But I recently completed a project, and after export, I try playing the video through QuickTime and the video is sooo terribly laggy and choppy. It's not handling it at all.

I have no other apps open, my software is up-to-date, and when I play the video on my iPad Pro 11 (4th Gen), it plays perfectly fine and looks great. I understand that my iPad has a M2 chip but seriously... I would expect that my MacBook should be playing it fine.

What is the issue? The video is 4k MP4 H265. My heart is breaking here, please help. I'm hoping I'm just doing something wrong.

Thanks.