Why do you imagine the ragged man with the silver pipe invited the children “to come to the candy mountain” in Milkweed?

The piper is mentioned several times, weaving through the streets calling to the children to come to the “candy mountain.” Janina finds this tempting, but her father tells Misha there is no such thing.
During the time the piper is doing this, the Nazis are routinely conducting roundups of Jews and sending them off by train. Although the adults have some idea about the death camps, they try to protect the children. Because life has gotten so horrible in the city, where there is no food, people are desperate to leave and the children do not understand the greater dangers elsewhere.
Janina associates the trains with the mythical candy mountain and tries to hold on to her fantasy. The piper is not a Jackboot, so it seems unlikely that he is complicit in the deporations; rather, he seems to have become deranged. He may in his mind believe there is hope for the children to escape, or he may be living completely in his own fantasy world. Thus the candy mountain could represent many things, such as hope, fate, the futility of escape, insanity, or death.