Of all places, why Dagobah? What makes Dagobah so safe or comfortable for him?
According to the new Star Wars: Absolutely Everything you Need to Know, Dagobah is ideal because it's
Shrouded in clouds, thick with fog and far from the civilised galaxy,
making it the
perfect refuge for a Jedi Master in hiding
It also mentions the planet's extremely high levels of life (allowing for a greater connection to the Force while he meditates on the downfall of the Jedi) and the Force cave which shrouds his light side Force from the Emperor.