Desert plants mainly bloom at night due to their adaptation to the desert environment. Here`s how each option relates to this:

Option 1: While it`s true that desert temperatures drastically drop at night, it`s not the main reason for nighttime blooming. Some flowers do indeed open when it is cooler, but this isn`t the overriding factor for desert plants.

Option 2: Sensitivity to moon phases does affect some creatures but isn`t particularly relevant to plants. Plants aren`t known to have specific responses to moon phases that affect their blooming.

Option 3: Insects might eat flowers during the day, but most flower eating insects are also active at night. This would not contribute to the desert plants` preference to bloom mainly at night.

Option 4: The primary reason desert plants bloom at night is to attract pollinators which are active during the night. Most desert insects are nocturnal, as the desert is cooler and predators are fewer. Therefore, by blooming at night, these plants enhance their chance of pollination.