Just like any phone battery catching fire, a lot of factors can play into this. And no, iPhones are not immune. It’s just the nature of lithium ion battery.Who can we blame?
Some possibilities:
- improper charging. Be it from random chargers or even an airplane’s own USB port. Coupled with bad cables, things can happen.
- manufacturer defect. In the end, these lithium batteries are mass produced. Even Apple had recalls on batteries for iPhones and MacBooks. Human made stuff will never be 100% perfect.
- design defect. Clear example is the Note 7. Unfortunately, on the lower end models, Samsung does outsource them (designs and everything) to ODMs, and slab Samsung brand on it. Not sure if the A21 is one of these, but A10 or lower were definitely ODM, not Samsung original design.
In any case, nobody knows at this point.