The theme itself doesn’t have control of video autoplay or not.
As far as I know, most mobile devices, including Apple iPhones, Apple iPads and many Android and Microsoft devices do not support the video autoplay feature so your video will not play automatically if a visitor is on one of these devices.
You can try switch to twenty-twenty one theme to test if the issue still there.
I thought that too! Then I saw this website on my phone and I was surprised beccause it autoplays on my iphone. Any idea how it’s autoplaying on phone?