The best path to prosperity and high wages is a dynamic and robust economy where pretty much any worker can walk across the street and be hired for a better job on the spot if he or she thinks she is being underpaid or poorly treated.
1. Union labor became so expensive that employers had to figure out ways to hire as few union workers as possible.
2. As you mentioned, union leadership has completely undermined the rank-and-file workers.
3. Unions began pushing for government policies like entitlements and government-run health care that basically gave people the kind of things that unions used to bargain for on behalf of their members. Who needs a union when you can just get Nancy Pelosi and Barack Obama to give you free sh!t even if you're not employed?