A video that you should check out is The Silver Shields by Invicta. They were elite veterans before Alexander was crowned, fought in many battles during his campaigns and fought as a unit years after his death. Decades of frontline combat experience.
I do believe that Alexander was probably assassinated by Cassander and a group of like-minded conspirators. As we already know, there had been multiple conspiracies against Alexander's life during this campaign. He had alienated not only many of his own soldiers but also many of his officers as well. Political assassinations were extremely common in the ancient world, and this is especially true within the Macedonian court. Alexander's own father, Philip, had been assassinated as well. Not to mention, he was later responsible for killing Alexander's mother, wife, and son. Additionally, poison was a very effective method of assassination since it left behind little evidence to implicate its perpetrators. During the Roman Empire, the Emperor Nero supposedly made use of a poison maker named Locusta to assassinate two of his political rivals including his step father Claudius and his step brother Britannicus. So, this type of thing was very common.
Also, it's worth mentioning that just because the author of a source may have a political motive to defame certain opponents doesn't necessarily mean the account is false, either. It does seem like a tremendous coincidence that he grew extremely ill and died a few days after the drinking party. If it was alcohol poisoning, he would have died before that. Granted, a lot of people back then died from very common or largely extinct diseases to us. It's certainly possible that was the case. But if I had to bet on it, I would wager that he was assassinated.
