Why are multiple engines different?

In article ,
Mxsmanic wrote:

Why is flying a multiengine aircraft a separate certification from the
basic license (if I understand correctly)? What is so different about
having more than one engine that justifies a separate certification?
Apart from a few procedures for the failure of an engine, isn't
everything else pretty much the same?

Does this mean that it is not possible to study for an initial license
in a twin-engine plane?

Perhaps it's because if you screw the pooch on those "few procedures for
the failure of an engine" you will be dead.

The only thing that would keep you from getting your initial certificate
in a multi would be money. (insurance and the nerve of your CFI may
factor into this also)