So while I’m sure someone more versed in Roman history could give you a more detailed explanation of the politics & economics of the Final War of the Roman Republic, I’d like to address more some popular misconceptions about Cleopatra.

First, we have no reason to believe that Cleopatra was not an incredibly successful leader. She ascended to the throne at the young age of 18 and ruled for 21 years, fighting off threats to her power both from inside her country, and outside it. Egypt flourished under her reign. Cleopatra herself was multilingual, and known for her political prowess. The primary reason she is remembered otherwise is because her tomb has remained thus far undiscovered, and there exist next to no records of her reign that would have been produced during her lifetime (with the exception of coins bearing her likeliness). In fact, the only historic biographic account of Cleopatra is found in the work of Plutarch (Parallel Lives), in which she is mentioned within the biographies of Julius Caesar and Mark Anthony. It is from these accounts of Plutarch, and the various literary accounts that follow, in which Cleopatra becomes immortalized as the ‘oriental femme fatale’ in the western tradition.

It’s worth noting that despite becoming a sex symbol of sorts, Plutarch doesn’t even eulogize her as being remarkably beautiful, “For her actual beauty, it is said, was not in itself so remarkable that none could be compared with her, or that no one could see her without being struck by it, but the contact of her presence, if you lived with her, was irresistible” (Plutarch, Biography of Anthony). The biggest issue is that the works of Plutarch are written well after the fact (Almost two centuries later, given that Cleopatra died in 30 BCE and Plutarch’s Parallel Lives are estimated to have been published in the beginning of the 2nd century CE) and are rather dramatized. His preference is clearly towards the male romans who are “corrupted” by Cleopatra. It makes his accounts of her to a particular extent unreliable.

As for Egypt's downfall, Cleopatra suicide coincides with the end of the final war of the Roman republic, a civil war notably between Octavius and Cleopatra alongside Mark Anthony. After Cleopatra’s death and thus defeat, Egypt became a Roman province and by no means “fell apart.” It was one of the wealthiest Roman provinces. It was just no longer independent from Rome.

For a short list of some further reading on the topic I would suggest the following:

Cleopatra: Beyond the Myth by Michel Chauveau (original French: Cléopâtre: au-delà du mythe)

Cleopatra: The Search for the Last Queen of Egypt by Zahi Hawass and Franck Goddio

Egypt After the Pharaohs, 332 BC-AD 642 by Alan K. Bowman

https://www.smithsonianmag.com/history/rehabilitating-cleopatra-70613486/

Edit: word choice