1. Things don't actually need to be fast, they only need to appear fast (cache, progressive update, etc), there are a hundred other factors that would determine software success.
2. Any language worth a shit has FFI to handle extreme cases of pareto's principle that need to be solved in the constant time interval.
3. Since speed is absolutely everything Lotus 1-2-3 continues to bask in the dollars as everyone waited for them to port an app COMPLETELY WRITTEN IN ASSEMBLY to Windows, while Excel has been left to rot for being just barely Real World performance grade in the early 90s. oh wait, no.