your power-regulator (an lm2596s IC) is burned out. it converts the 24AC (with a few diodes) to 5VDC for supplying power to the raspberry PI.
My educated guess is that your main power-supply had a (short) voltage peak. the transformers aren’t protected to that (it’s by design, because it’s AC to AC).
You can try to fix it, replace the lm2596s IC and probably also the PTC fuse (green component to the left of your burned IC).
But that’s only possible if the fuse worked. so the high voltage is stopped by the fuse.