He had been battling cancer for some time apparently, was not aware he was sick. Shame he passed before he made it into the HOF
Some people prefer to fight those battles quietly. His terrible leg injury is one of the first thoughts that come to mind when thinking of Psycho Sid along with his crazy eyes/face and water/sweat on his face and/or hair as he was frantically turning his head in different directions.
Since you mentioned the HOF... The concept of the WWE HOF is a little weird when a scripted sport has people deciding who should be in the HOF and when they should go in the HOF with no rhyme or reason behind their decision. Some wrestlers greatly appreciate being added to the HOF and others aren't as concerned or could care less and I have no idea where on the spectrum Sid fell.
That said, if HHH or anyone that is able to make HOF decisions or pitches was aware that Sid was battling cancer for years and felt he was worthy of the HOF then he should have been inducted while he was alive. Inducting someone after they pass away when they were fighting a lengthy illness is bullshit. Some pass suddenly and it's out of your control but in a way I hope Sid was one of those that felt it didn't matter if he was in the HOF or not or is never inducted so he didn't miss out on the potential honour.
Rest well to the master and the ruler, of the world.