Yes, everyone deserves a second chance providing that they are truly sorry for what they done and don't do it again, but they don't deserve a third, fourth or fifth chance (as he had five convictions)
The sentence is as astonishing as the story
If the previous convictions were spent, the railway wouldn't have even known about them.
The only previous conviction mentioned in the article was a common assault from 2009 which would have likely both been spent by the time he joined the railway (unless he's been working there a long time), and if he joined after 2000, it would've even be filtered off of Standard and Enhanced DBS checks under the filtering rules.
He now has a GBH conviction though, which will never be filtered off Standard and Enhanced DBS'. I imagine most trackside workers only require Basic DBS' so in a little over 5 years' time he could potentially end up rejoining, but I imagine that in 5 years' time a lot of employers will be running some magic AI software to do background checks and find this story.
Basically, I'd be surprised if he'll work on the railway after this, but there's a fair chance the railway had no idea about his past convictions when he joined because it sounds like they were minor and from a while back and therefore probably spent.