Reason: Realisation & WH– Probe

Halliday & Matthiessen (2014: 321):

A circumstantial expression of Reason represents the reason for which a process takes place – what causes it; they have the sense of ‘because’. It is typically expressed by a prepositional phrase with through, from, for or a complex preposition such as because of, as a result of, thanks to, due to; also the negative for want of … 

There is also one class of expressions with of, one of the few places where of functions as a full preposition (ie representing a minor process) as distinct from being merely a structure marker; for example, die of starvation. The corresponding WH– forms are why? or how?.