Why did Old Major wish to speak to the other animals after Mr Jones went to bed in Animal Farm?

Old Major wishes to speak to the animals after Jones
retires for the night because what he has to say is an indictment of the rule of human
beings.  Old Major wants Jones to be asleep so that he can speak to the abuses of
animals at the hands of men.  Old Major waits until Jones goes to bed in order to freely
express his thoughts that both deconstruct the present system on the farm and articulate
a vision of the future.  The deconstruction lies in Old Major's beliefs that the animals
are exploited by the human beings.  He argues that the animals are used and abused,
useful only to humans in so far as they help to generate profit.  When the animals have
outlasted their usefulness, Old Major argues that they will be slaughtered.  In addition
to this, Old Major speaks of a vision whereby the animals are able to assert control of
their own destiny.  He renders a vision to the animals in something called "Animalism"
whereby humans are the enemies and all of the animals work together as one common
entity.  Old Major has to wait unti Jones slumbers in order to speak of both visions as
they represent a direct attack on Jones as a manager.  In doing so, Old Major sets the
wheels in motion for both revolution and the themes of Orwell's
work.