If you search this forum for "false vivipary", you will find quite a number of results of threads with photos:
search.php?keywords=false+vivipary&term ... mit=Search
The mechanism that causes this isn't well defined, at least to my knowledge. It is likely some sort of plant growth regulators (PGRs) that are sometimes released during flowering that results in the flower stalk growing plants on the forks of the flower stalk. It could probably be promoted by directly applying PGRs to the flower stalk.
In any case, I've never seen a bunch of plants doing it all at once like this. Very cool! Perhaps whoever grows those plants used PGRs to make it happen. Or the plants in the photo were all growing in the same conditions and thus released the hormones that caused false vivipary to happen. Either way, it is awesome to see!
Leave the meat for our pet plants