It will depend on the specific plant but succulents and cacti are often pollinated by the same creatures that pollinate other outdoor plants - bees, flies, wasps, butterflies, etc. And birds and bats!! Bats - and moths - are big for night blooming succs like saguarro or cereus.

I recall a January stroll through the Desert Garden of the Huntington Botanical Gardens in San Marino CA and having to dodge the hordes of hummingbirds that were visiting.

Wow, that sounds exciting! I’ve visited a number of botanical gardens that had cacti & succulent exhibits, but they were all indoors, so no pollinators.

You need to Google your favorite plants in regards to their pollinators. Don't use such a broad term as 'succulent' in your search, but be specific.