More speculation and assumption. All the suggestions are assumptions. You have no evidence to show it actually happened. Evolution is full of that.
It has been explained to you previously that using magic words like "speculation" and "assumption" is:
1. Not actually addressing the evidence.
2. Does not make the evidence somehow not evidence.
3. Does not poof the evidence away in a cloud of smoke.
You need to actually address the evidence, not just repeat Creationist magic words.
Take a look at the Emetazoa article and break that down in plain English for the common folk. Wonder if you really can or if you just posted a bunch of stuff you have no idea what it says.
Title - Colonial origin for Eumetazoa (the title is a typo)
Meaning - True animals evolved from early colony beings
"These transitions included the origins of Metazoa, Eumetazoa, and Bilateria and involved the successive development of poriferan, cnidarian, and bilaterian grades of organization."
Meaning - the origins of animals involved sponges*, then true animals followed with jellyfish* followed by bilatarian body plans for, axiomatically, bilaterians.
"In the model offered for the cnidarian-to-bilaterian transition, the last common ancestor of Eumetazoa is considered to have had a colonial, cnidarian-grade of organization."
For the evolution of jellyfish to bilaterians, the population that gave rise to that spilt (basal true animals) would have had a colony type, jellyfish style body plan.
"Whatever its cause, the individuation of a cnidarian-grade colony furnishes a possible explanation for the rapid diversification of bilaterians in the late Vendian and Cambrian."
An explanation for the development of Ediacaran fauna and the Cambrian explosion can be explained by jellyfish type colony beings developing a variety of body plans.
* I'm using common example beings for porifera and cnidarians.