How does the union movement

amass a $1.5bn "war chest"? 
Union membership is falling but it seems that unions are still doing extremely well with respect to money.  Apparently the new source of money is "superannuation".
To say that I am appalled they are using the money of their members in this way is putting it mildly. Superannuation funds are supposed to be there to provide for income support in retirement. They are not there to provide funds for political campaigns - even if you agree with what they are campaigning over and the way they go about it.
Union membership was once compulsory for many people. It was "no ticket, no job". Paying  union dues was something you expected to do. In a sense it was another form of taxation. 
Unions also had a job to do. They would argue they still have a job to do.
Realistically though union power has declined along with membership. There are other means of ensuring that the rights (and privileges) of workers are protected. There are tribunals and commissions involved. The courts have more power because of legislative changes. The mainstream media and social media can put great pressure on employers to do the right thing. 
That doesn't mean that unions have nothing to offer. They still have a role to play. It is just that it is no longer the role that it once was. It has altered. Their power has diminished in some areas - and rightly so. Their purpose in others - such as Occupational Health and Safety training - should have increased. They should not be seen as the alternative government or have the right to dictate to employers how things will be done.
Of course they would still like to be seen that way and as having that power but things have changed - and they must remain changed.  
That $1.5bn should be used for the benefit of members. It should not be used so that a few at the top can grab power and  use it to dictate to the rest of the country.  That means putting the money to work to build up the money workers will have to live a more comfortable retirement. Anything else is theft.