Hello, 2Kay, and welcome to the Grammar Exchange.
The poignancy is palpable because of what we know is going to happen.
Which one is the subject of "is going to happen"?
The subject of "is going to happen" is "what." The free relative clause "what we know is going to happen" functions as the object of the preposition "of." That free relative clause contains another clause, complementing "know." "What" is the subject of that clause: "We know [what] is going to happen."
P.S. Please read the Guidelines page to learn how to write a good title.