Salam Alaikum, it's true that the Prophet died because the affects of poison? (which seems to have many flaws) Or did our Prophet die because a natural cause?
There's reliable ahadith that the Prophet was poisoned after the Battle of Khaybar:
An important point here is the long time difference between when the Prophet was poisoned (in the year 628), and when the Prophet died (in the year 632).
Ibn Masud (Allah be pleased with him) felt that the Prophet [peace be upon him] had died as a martyr, the delay in the poison’s effect being a prophetic miracle. Allah Most High thus preserved His beloved Messenger until his mission was completed, and then, to honor him, caused him to die a martyr. [al-Zurqani, Sharh Mawahib Laduniyya]
Abdullah Anik Misra, SeekersHub
This conclusion is supported by the hadith:
Narrated 'Aisha: The Prophet in his ailment in which he died, used to say, "O 'Aisha! I still feel the pain caused by the food I ate at Khaibar, and at this time, I feel as if my aorta is being cut from that poison."
Sahih al-Bukhari 4428
In any case, it's not as straightforward as "he was poisoned to death".
There are alternative scholarly views:
In conclusion, it seems most likely that the Prophet (pbuh) died of natural causes and was not poisoned. And God knows best.
Sheikh Mansour Leghaei, Ask The Sheikh
This later view appears in Shia Islam:
Several prominent Shia accounts even report that she, along with Hafsa, brought about Muhammad’s death by giving him poison.
Shia view of Aisha, Wikipedia