Maybe, but will they have to fight with borrow checker for doing some other than (the very OOP) DOM components? They'll obviously use both for a long time in the future, so more functional places can get Rust, while more OOP places can benefit from C++
And? Does it work? Because it does. It's a lot closer to C++ and you literally need like a week to start being productive and it's insanely flexible as a language. Nobody uses Swift also, but the additional problem with Swift was that it's entirely Apple-centric.