# Trouble understanding how Naive Bayes Classifier is derived

I've come across the Naive Bayes Classifier while studying machine learning, but the trouble I'm having is with some of the probability theory used to derive the formula for finding the optimal classifier, which is why I've posted this question on mathstack(if mathstack is not the appropriate for the question, please direct me to the correct site).

My lecture slide is very unclear on how the optimal classifier is calculated:

Given a training data set $D$ with $n$ instances, $e_1$,...,$e_n$, where each instance $e_i=(x_1=v_{i1}, x_2=v_{i2},..., x_m=v_{im})$ is seen as an attribute($x$)-value($v$) pair. And given a set of hypothesis $H$, $h_{MAP}$ is defined to the most probable hypothesis from the set $H$ given the training data set $D$, i.e the optimal classifier.
I'm not sure what the lecture slides mean by i.i.d, but I'm pretty sure that the $e_i$'s are the individual instances in the training set $D$.
Therefore, $h_{MAP}=argmax_{h_j\in H}(p(h_j|D))=argmax_{h_j\in H}(p(h_j|e_1,e_2,...,e_n))$ I'm unsure what the bullet point is trying to say, if all hypothesis are equally likely, then $h_{MAP}$ is the maximum likelihood hypothesis, and because of this claim, the notes suddenly assume that
$p(h_j|e_1,...,e_n)=p(e_1,...,e_n|h_j)$
but, by Bayes rule:
$p(h_j|e_1,...,e_n)=\frac{p(e_1,...,e_n|h_j)p(h_j)}{p(e_1,...,e_n)}$
I haven't done much stats, so I'm sorry if the question is obvious, but how does the assumption that all hypothesis' are equally likely, lead to:
$\frac{p(h_j)}{p(e_1,...,e_n)}=1$, for all $j$
Would it always be the case that $p(e_1,...,e_n|h_j)=\Pi_{i=1}^{n}p(e_i|h_j)$, or have the notes implicitly assumed that the $e_i$ are conditionally independent. Now the slide has assumed that each instance $e_i=(x^i, v^i)$, but each instance doesn't have a single attribute, so I'm guessing it's a bad representation of what I've assumed, i.e. $e_i=(x_1=v_{i1}, x_2=v_{i2},..., x_m=v_{im})$, unless I'm wrong, then can someone please correct me. Because the equation for $p(e_i|h_j)$ makes no sense to me.

The notation $\mathrm{arg}\ \mathrm{max}$ indicates that the left hand side is the tuple of argument values that yields the maximum value of the function.