Isn't Lisp 5-20 times slower than C/C++/Rust ( https://benchmarksgame-team.pages.debian.net/benchmarksgame/... )? Performance is important for a browser.
It depends on how you write the code and the compiler you use, but Lisp can be as fast as if not faster than C. But the main thing is that in Lisp it's easy to turn the dial between speed and other things you might want to optimize for like safety and debugability. Making C code memory safe is a lot of work at best, and actually impossible at worst.
Could you point me to some benchmarks of Lisp being comparable to C?
Also, unless I am mistaken, Common Lisp doesn't have strong types. How can you make either fast or safe language without compiler knowing the types?