Can I get a TLDR of why Proa is seemingly so much faster tha existing Rust web frameworks (Dioxus, Leptos, Topcoat)?

I can't speak for the others as I am not as familiar with how they're engineered, but with Proa I spent a painstaking amount of time to try and move as much of the work to compile time as possible and being really careful about how memory is allocated. And a lot of those small improvements add up over time!