Try bending the end with a barbed hook like a tick shape and see if that holds .Every time I do they they pull out the loose soil lol
looks like there ropes into the ground ,I’ve seen tomato growers plant rope under the plant the grow it up before
my pet hate is do I drill holes in buckets ,build cages . Or whatever mad contraption I find to pin them down
this looks really tidy
Otherwise you could use 2 spring clips attached to opposite edges of pot and pass a skinny dowel through the handles of the clips and hook a S shaped bit of wire under dowel and over branch