Here's why:

* Meiosis is the process that creates haploid gametes (sperm and egg) from a diploid cell. Each gamete has half the number of chromosomes as the parent cell.

* Fertilization is the union of two haploid gametes (sperm and egg). This fusion restores the diploid number of chromosomes, creating a zygote.

* The zygote is the first cell of a new diploid organism, which will then continue to divide by mitosis to develop into a multicellular organism.

So, while meiosis is essential for producing the gametes that will eventually form a diploid organism, it is the fertilization event that actually creates the diploid organism.