Why
was the Praja Parishad formed?

It was formed to start a revolution.

Explanation:

The organization was formed in the 1930s. Tanka Prasad Acharya led the formation of this organization, and the main goal was an attempt to overthrow the Rana dynasty, which was the undisputed ruler of Nepal. The organization was demolished, and the attempt failed when the authorities discovered the existence and purpose. Some members of the organization were killed, and quick action by the authorities arrested some.

so, based on the research i've done. the u.s. government were always on a wild goose chase just to take down castro. he then retired his trone to his brother raul in 2008 due to some health issues. so it's obvious your answer would be:

castro had no allies from which he could receive aid.

hope this and have a fantastic day!

                                                    -wolfiewolffromsketch