Swift does implicit allocations, doesn't have explicit monomorphisation, requires a non-trivial runtime. Language functionality like ARC and ivars compiles to a lot of "magic" (compared to Rust's focus on zero-cost abstractions). Swift's standard library is full of dynamic dispatch (e.g. Swift strings are a collection of classes with abstracted-away and variable in-memory representation. Rust's strings are dumb pointer+length).

Swift is much higher-level than Rust. It's at best at Go's level. You'd expect Swift's performance to be good, but in low-level tasks Swift is actually closer to JS/TypeScript than anything else: https://github.com/ixy-languages/ixy-languages

I'd be careful about drawing general conclusions from https://github.com/ixy-languages/ixy-languages

It's using some non-optimal patterns that you would not normally use in Swift for code if you wanted it to perform well. (There's a nice performance analysis if you click in, showing that it's using ARC in an inner loop, which is taking 3/4th of the time. That's not something you need to do.)