You connected the battery backwards perhaps? The output cap won't have seen 50V, so driving it backwards is the only likely way to
vaporize its innards quickly. Might be other damage too if that's the case.
Or some other component failed upstream?
Until you fix the obvious damage it'll be hard to tell.
You should always use a fuse inline with lead-acid batteries BTW, they can put out destructive currents if accidentally
shorted.
Find high-temperature electrolytics if you can to replace them, they will last a longer.