Speedy obviously lost his mind in all the years he spent trying to escape the island; pranking people as "the ghost". He missed the fact that the prison had be shut down for some years and he could have hopped on a vehicle to leave. Paying in mind he would have to subsist off the sea food and plant life, its obvious something didn't agree with his brain.
The fact no one ever caught Speedy, despite his age, implies there were no cameras in Alcatraz.
Speedy technically should have already outlived his sentence. Seeing as he would have been imprisoned in the 1960s. Plus Alcatraz wasn't a prison for a good chunk of time between the 60s and 90s.
So getting him pardoned was pointless.
So getting him pardoned was pointless.