The connection is simple to understand. Unions are still run by crime syndicates, unions finance Democrats almost exclusively, therefore Democrats do what they are told to do by the crime syndicates.
How do I know that unions are still run by crime syndicates? It is because when I was growing up in Chicago I went to school with that generation of crime syndicate kids. Many of the guys I went to high school with are now in management positions in the unions.
The strong connection between crime syndicates and the Democrats goes back over 60 years. It is well-known that Joe Kennedy (JFK's father) made a deal with the crime syndicates and unions to support his son in the 1960 election. In return, Joe promised that the Kennedy administration would allow them to build their crime organizations unfettered. It turned out that the 1960 election was the closest election in our history, but perhaps one of the most fraudulent election in history (#2 after the 2012 election). Over 10,000 dead people voted in Chicago in 1960. Nixon may have legitimately won that election. But after JFK took office he reneged on the agreement. When his brother Bobby Kennedy became Attorney General, he aggressively prosecuted criminal organizations. That is one of the many reasons why there is a strong belief that the crime families were intimately involved in both the JFK and Bobby Kennedy assassinations.
At the time there was a joke going around Chicago. "My grandfather was a staunch Republican his entire life, but since he died, things have changed. He now only votes for Democrats." The problem is that this wasn't a joke.
A small number of Republicans have also had crime syndicate connections. Spiro Agnew, who was Richard Nixon's first vice president, resigned over allegations about his crime syndicate connections and bribes he allegedly accepted.
"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -- Benjamin Franklin