The (now deleted but since restored) answer you were originally given has the right of it, it was a good one, I'm not sure why @b.nota deleted it.
There is a general rule that you pot up only one or two sizes at a time for plants, but there are exceptions, which are fast growing annual plants that are expected to produce fruits during the relatively short period of summer. Your basil is not expected to produce fruit, it is grown for its leaves, and is only a relatively small plant when compared with, say, a tomato plant. When a plant grows rapidly and puts on topgrowth in preparation for fruiting in the same year, the roots also grow quickly and rapidly take up space in the large pot you've used. But if you put, say, a small seedling of a non fruiting perennnial plant such as lavender in a very large pot immediately, the roots don't grow quickly because the plant doesn't get that large and isn't such a fast grower, it's a shrub. That means the potting soil is largely unoccupied, and you would need to keep it wetter in order to ensure the small amount of roots actually receive any water at all. And a large amount of unoccupied, wet potting soil is prone to souring and may become unhealthy for its small occupant, and fungal problems are likely. This also applies to most houseplants, since they are not annual, rapid growing, fruiting plants either.
Therefore, if you want to grow, say, a tomato or a pepper, then, when the seedling has developed into a small plant, they should be potted straight into the large container they will stay in until the growing season is over. But a basil plant, or, say, an indoor Schefflera or Sansevieria should not be put straight into a large container for the reasons explained above.