I'm with DB74 on this one.
There are too many 'circumstances' but not enough hard evidence to prove foul play.
As to whether a muslim can become monarch, I don't think they can at the moment, it's written into the constitution. Neither can Roman Catholics become monarchs (I think this is still in force) but anyway, had it happened (a very remote possibility as slugga has explained), Dodi would only have been a Prince Consort like Philip is now.