My point is that the WEI proposal is trying to solve a genuine and increasingly important issue for providers on the web. And, there's at least a possible outcome where we have many trusted providers that maintain the core parts of the open web that we love while giving these providers some better solution than what exists now.
As for why would they trust Brave? I imagine it'd be similar to TLS now, where website owners probably wouldn't even think about this and they'd just use CA chains provided by browsers, operating systems, etc.