I got lost in the sauce a bit. The tweet is still comparing different statics. Chernobyl had less then 100 deaths in the first year, but thousands more deaths from cancer in the following year. Those were excluded from mention.

Bhopal had 16,000 deaths in the first year and 500,000 "nonfatally poisoned" casualties. Those almost certainty lead to premature deaths and if we're including those, we also need to be including the long term cancer deaths from Chernobyl.