[Consort]

Well, no. The subject of the sentence is the singular pronoun what. It does sound odd though.

I think it can go both ways:

"In some cases, you can treat a clause with what as the subject as singular or plural, depending on the emphasis you want to convey. In What excite him most are money and power, the implication is that money and power are distinct elements; in What excites him most is money and power, the implication is that money and power are a single entity...,"

More info and examples are provided here.

[Principled]

Yes, it can go both ways. It was correct.

[Bonaparte]

"What excite him most are money and power"

I've seen that constuction used before but not by professionals. It's awkward. Best to just go around it.

Money and power excite him most.