'' Has commited suicide '' on Infernalist witch

I don't understand how I died here?, my life flask has '' Increased amount recovered and Gains 0.15 charges per second ''
https://streamable.com/96lp2z

Have you even read what infernal flame does?
Specifically this part:

Maximum Mana is replaced by Maximum Infernal Flame
Gain Infernal Flame instead of spending Mana for Skill costs
Take maximum Life and Energy Shield as Fire Damage when Infernal Flame reaches maximum

probably GGG needs to put a huge warning in red letters YOU CAN DIE FROM THIS lol

Your Infernal Flame filled up three times in a row, each one smashes you for your Max Life + Max ES. So you chewed through three health bars in roughly 3 Seconds, not letting your Infernal Flame cool down, or your ES recharge, either of which would have done the trick. Feels like you haven't played that character before, not a fight I'd suggest taking a new spec into.