Maggots start up in any corpses if flies have the opportunity to bring their larvae onto it, which will feed on the decaying remains of the body.
A small clarification to the previous answer, could not resist. Maggot is the larva of a meat fly . In nature, the best breeding ground for them is any rotten, that is, fermented, meat (you can fish, the main thing is animal origin). Even considering his diet during life, the vegan's corpse is meat, and he will not become a plant, even if he really wanted to. So maggots will gladly settle on it in order to take part in the natural biological process of decomposition of the body.
And in the photo you seem to have a mealworm.
Maggot is a fly larva, it appears on any carrion that the flies choose, regardless of what this corpse ate during its lifetime.
In any case, on cows, they appear wow, in spite of the plant diet.
Unless a vegan will bring himself to an extreme degree of exhaustion and self-mimicate like some Buddhist monks