This makes me think of a research paper that cognitive scientist John Vervaeke wrote on wisdom vs foolishness:

https://www.researchgate.net/profile/John-Vervaeke/publication/286508333_Relevance_Meaning_and_the_Cognitive_Science_of_Wisdom/links/58f529df458515ff23b56743/Relevance-Meaning-and-the-Cognitive-Science-of-Wisdom.pdf

See the diagram on page 13

Malvolio's self righteous personality is shown through this phrase. He mentions that "some have greatness thrust upon 'em," referring to his view that he is destined for nobility and eminence. He speaks of himself in third person displaying the egoism that he contains. After Malvolio finds the letter that he believes was written by Olivia, he automatically assumes that it is from Olivia and that its true that Olivia wants him to declare his love. This displays the theme of how desire can make someone a fool. Malvolio's egoism as well as his desire for Olivia makes him do all of the foolish things that the letter told him to.

Malvolio acts quite foolish about his desire for power. Malvolio is delusional as he is imagining himself as someone who will be wealthy and powerful. His head is too far into the future to be able to achieve his goal, which why he was able to fall for the letter. This is evident specifically "having come from a daybed where I have left Olivia sleeping." He is not married to Olivia and imagines a scenario where he is. -Owen, Simone, Janely