I don't think terrorists have elastic morals; Islamist ones, at any rate, seem to have seriously perverted but very rigid morals.
As for Islamic involvement in finance, The major Islamic countries go to great lengths to make their banking and finance sharia-compliant. https://en.wikipedia.org/wiki/Islamic_banking_and_finance
Not sure where you got that idea that they have rigid morals. Like most people they may be rigid about a select few rules such as praying or belief in Allah but pretty lax about others eg drinking, taking drugs, killing people to pursue a political agenda. Islamic Terrorists are much like other people who kill for a cause or a mission - eg armed forces - so no different to the IDF for example- they are trained to complete a job. If it’s perverse to kill and terrorise people for political reasons- it seems to be a widespread perversion shared by most governments and armed forces. Why is it perverse if terrorists do it but not if governments do it?
The people who train terrorists / militants / armies are usually pretty cynical- ie they can see all governments lie and kill and are corrupt, some more than others, so they are just another actor in the political arena trying to protect certain interests important to them.
