I think it's cynicism in some people, but I'd argue it's more just mellowing of opinions over time.
The video shows this pretty nicely; we have younger Joe Hockey as a progressive, nowadays he's a key member in a highly conservative government. Conversely, we have Malcolm Fraser who headed up a fairly conservative Liberal government and is not endorsing Greens candidates in later life.
Essentially, people's opinions change over time because what is important to them changes over time as well. Early 20's Uni Student Joe Hockey understandably cared about university fees; late 40s Politician Joe Hockey is obviously more focused on other things. I wouldn't call it hypocrisy because he's (assumedly) not advocating for something he doesn't really believe in - he likely wouldn't be Coalition treasurer if this were the case. Simply put, his priorities have shifted, just like Fraser's has.
Side note: I feel like that this is an inherent weakness in democracy, in that those generally representing the population aren't often actually reflective of the strata of populations they represent due to age gap and resultant differing of interests.