Contrary to its claims of being unarmed, it was straight-up the leading supplier of munitions to the rebellion, pretty much the opposite of unarmed.
In the novelization, yes - which also had multiple Emperors, of which Palpatine was only the first - and with the current Emperor being controlled by his advisors.
Safe to say that things changed.
"During this time, Alderaan became the Alliance's main source of munitions. The planet's crown princess and representative in the Imperial Senate , Princess Leia Organa [2] , adoptive daughter of Bail and Breha Organa, began using her diplomatic immunity as an Imperial senator to carry out Rebel missions in restricted Imperial systems. [19] About three years before the Battle of Yavin , Senator Bail Organa dispatched three Hammerhead corvettes to the Phoenix rebel cell , which has sustained losses while fleeing Garel ."
From Wookieepedia. I assume most of it is sourced via Rebels, which is fully canon.