In the begining of Parshat B'shalach, Rashi says that one p'shat for "Vachamushim" means one fifth, because during Makas Choshech, 4 out of 5 were killed out, and it happened during the time it was dark so that the Egyptians shouldn't see (although, I'm sure once that darkness went away,they would have noticed a HUGE difference in the Jewish population). If you do the math, 600,000 went out of Mitzrayim, which means that four fifths = 2,400,000. My question basically is, why is there no mention of this anywhere? Why were these people killed out? Why are we celebrating the g'ulah of 600,000 while 2.4 million were killed out? This has always bothered me.....
The Jews that died, did not want to leave Mitzrayim.