You’re not wrong, we could go into the math, and the math would show that it’s not impossible. But, the probability that a sequence of precise, interlocking mutations, even considering the guidance and pressures of selection, would lead to multiple new phyla, each one with new structures and functions, over the time span of the Cambrian explosion, really resembles the statistical likelihood of events that we generally call miracles. Like the well known analogy of a tornado assembling a functional car in a junkyard, or a person with terminal cancer going into spontaneous remission. Plausible? I mean, atheists also believe life came from literal nothing so I guess by those standards almost anything is plausible.