I figured he took the train out of fear of being shot down. The train is heavily armored and bomb-proof, so it is more protected than an airplane. He is probably also aware of the attempt to take down Trump's plane the last time they met.
Looks like they killed him exactly 3 years to the day of that tweet.
wikipedia.org/wiki/Prodigy_(rapper)
It just gets more and more ridiculous:
"The late Mobb Deep rapper Prodigy died after choking on an egg in a freak accident while he was in hospital receiving treatment for his condition of sickle cell anaemia, it has been confirmed."
contactmusic.com/prodigy/news/mobb-deep-prodigy-died-choking-egg_5779217