I think the delivery could be greatly improved by introducing symbols and clarifying the logical environment where the derivation is happening. Allow me to do this, without using LateX I'll assume /\ stands for logical conjunction and ~ for logical negation.

Proposition symbols

Our universe is normal: N
We exist: E
Our universe is magical: M

Logical environment

[1] The universe is either normal or magical: M = ~N
[2] The magical universe is strongly biased to support our existence: P(E|M) = 1

Derivation

By Bayes theorem:

P(N|E) = P(E|N) P(N) / P(E) <-->

P(N|E) = k P(E) /\ k = P(E|N)/P(E)

By partition of unity and [1]

P(E) = P(E|N)P(N) + P(E|M)P(M) => (by fact [2])
P(E|N)P(N) + P(~N) => (by law of probability)
P(E|N)P(N) + 1 - P(N)

If P(E|N) -> 0 with P(N) fixed (say c), we get

P(E) -> 0/c + 1 - c = 1 - c

From this

P(N|E) = k P(E) -> k (1-c) /\ k -> 0 / (1-c)

so that

P(N|E) -> 0