Some do and some don't. It's certainly not a traditional component of the Passover commemoration.
But for those who do include it, perhaps it's the following passage in the ancient text of the Passover
seder that inspires them to include the Holocaust in their recollections. It says "Not only one alone,
but in every generation they rise up upon us to destroy us, but the Blessed Holy One rescues us
from their hands."
yes, they tried to do as much as possible to follow their religion
There are always Jews who celebrate Passover regardless of the location or circumstances. Jews celebrated Passover in the ghettos, and then in the concentration camps.
Yes, because Passover is a Jewish festival. see also:What_do_Jews_do_when_celebrating_passover
Irish Jews celebrate Passover the same way as Jews all over the world.
Passover is usually only celebrated by Jews
German Jews celebrate Passover, too.
The same way that all other Jews observe Pesach (Passover).
Jewish people celebrate Passover to celebrate their people's liberation from slavery. The holiday celebrates when Jews were freed from slavery in Ancient Egypt.
Jews still celebrate Passover to this day.
There is no such thing as a "reformed" Jew. It is called "reform Jew". Reform Jews celebrate passover as a commoration of the exodus of the ancestors of the Jews from Egypt and into freedom, which is the same meaning passover has to Conservative and Orthodox Jews.
the event they celebrate passover is exodus
Non-Jews are not commanded to remember or observe Passover. Jews are commanded to remember and keep Passover (Exodus ch.12), and they should do so.