Although lightning is blistering, its radiant energy pales in comparison with the sun’s. While it’s true that lightning can set a tree on fire, the distance to its target must be very small for it to feel the full heat of lightning.
The sun’s core however is close to 15 million degrees Fahrenheit!
How about this fact lightning actually strikes UP not down. Invisible ion streakers rain down when the chemistry is overwhelming the electricity jumps up and lights up the streakers. Notice the heaviest part of the bolt is by the ground.