Translation:Without smart students, there won't be a better future.
Because it is how it is pronounced. It is pronounced "c", not any "st" or "ts" or anything like that. Etymologically it is derived from the adjective budoucí = future.
Also, there is nothing unusual about that. Adjective ending with -cí or -cný -> noun ending with -cnost. Mocno(st), jsoucno, vroucno(st), you can basically many random new words like this from any such adjective. The meaning is often quite abstract.