When Burnham arrived to the future (Star Trek: Discovery season 3),
she couldn't contact other sectors to inquire about whereabouts of USS Discovery because long-range communication wasn't working. This could possibly be one of the main reasons why Federation collapsed after The Burn because without communication, there could be no command or coordination.
But, why did long-range communication fail?
According to Memory Alpha:
The Burn was a galaxy-wide disastrous event that occurred sometime during the 31st century in which most dilithium mysteriously went inert, causing the detonation of every active warp core. The event caused widespread death and destruction, and led to the collapse of the United Federation of Planets.
Why would dilithium going inert cause long-range communication failure? What role does dilithium play in long-range communication device? I thought they are used only to control matter-antimatter reactions.