Why do terrorists fight?

It could be inferred the reason Muhammad claimed to have received revelations leading to islamic terrorism is to make wealth.

I used to wonder what was Muhammad's means of livelihood to sustain his so many soldiers and their many wives plus sex slaves. Here is the answer:

Narrated Ibn 'Umar that the
Prophet (SA) said, "MY LIVELIHOOD
is under the
shade of my spear,(1) and
he who disobeys my orders
will be humiliated by paying
Jizya" NOTE: "Under
the shade of my spear"
means "from war booty" .
Sahih Bukhari Vol.IV (page
104).

Like their prophet, muslims can take up weapons and rob people to make a living.

Look at Muhammad's exploits making money through spear:

http://www.thereligionofpeace.com/muhammad/myths-mu-raid-caravans.htm