The rationale here seems to be that by blocking video autoplay, Chrome incentivized sites shipping huge animated GIFs, or decoding video in JS and painting to canvas, both of which are very suboptimal for users.
Another comment points to this issue: https://bugs.chromium.org/p/chromium/issues/detail?id=106364...
quote:
Unfortunately, full autoplay blocking is counter productive as images and can do "video" playback just fine. We had this issue on mobile and ended up enabling muted autoplay there to avoid that issues.We found many websites having 100MB gifs that could be one order of magnitude smaller when implemented as .
endquote
This seems like a case of "the more you squeeze, the more sand trickles through your fingers?". Sites already have a way of always autoplaying muted video, but it involves either shipping 10x the bytes, or spending huge amounts of CPU and battery on decoding in JS.
Might as well let them autoplay muted video and save the user's network/CPU/battery.