What appears to be a long jump to a non-expert on first glance, on deeper inspection will usually turn out to have involved multiple small incremental steps culminating a final discovery. Since we have to acknowledge somebody we usually pick the guy/gal who finished the job. I'm not saying that all work is equal, but imho planning for long jumps is impossible (it's not like researchers don't want to make big leaps in understanding).
Examples which have changed my mind about this: Andrew Wiles' Fermat proof, evolution of RISC, quantum theories. I am pretty sure that if I dig into it, I'll find that relativity and evolution also built upon previous work.