A cynical take
Look all around you. It isn't just Millar who is changing position. Look at how riders and the media are repositioning themselves.
Just as Millar is suddenly growing a set to ask questions, so are various journalists such as CN, the clowns at AP etc
The cynical view is that they sense which way the wind is blowing. They sense that the UCI, McQuaid etc are on shaking ground and getting ever more shaky as the days get closer to the USADA report coming out.
It is easy to view this as cynical opportunism by Millar and sections of the cycling press, as bandwagon jumping.
Lampooning McQuaid and Verbruggen these days is like shooting fish in a barrel. The test is really questioning the new 'sacred cows' such as Sky, British cycling, Garmin, BMC etc
It isn't as if Millar has suddenly remembered that the UCI was complicit in creating a doping culture. Where was he 5 years ago? Where was he when Landis came out with his allegations? When Landis for example needed support from current riders where was Millar then? Now, all of a sudden with the USADA report due soon, Millar is suddenly finding his voice. The same can be said of the cycling press - where were they 5 or 10 years ago when Kimmage and Walsh were ploughing their lonely furrow?
In the end, you can take two views on 'why now'. Either Millar has genuinely found his voice and his belief and that it is only because he is towards the end of his career and the power of McQuaid and Verbruggen is waning that he can speak freely.
Or you can say that this is cynical opportunism from Millar and others - they realise that no one will really remember their past actions and praise for Armstrong as long as their most recent action is anti-Armstrong and anti-McQuaid. Millar has always been a politician and an expert at saying what the audience wants to hear - anyone who can remember his first articles when he started out in the late 1990s can remember that this has always been how he has conducted himself in public. This incident re-enforces the view that he is 'anti-doping campaigner David Millar'. Is it Millar positioning himself for a role in a post McQuaid cycling world? Hard to tell. It certainly doesn't do his public profile any harm. His comments about Armstrong were critical but also measured in a way that are unlikely to draw the ire of the few remaining Armstrong true-believers, especially when compared to his comments about Landis, or Ricco for example.
There is an old joke about you can tell how fast a revolution has fallen to the counter-revolution when the skinny revolutionaries stop appearing on TV and fat men in suits re-appear. The cynical would say that what we have here is members of the old guard re-positioning themselves and dressing themselves up as revolutionaries.
And this is the ultimate question about the future of cycling if McQuaid and the current UCI does fall, will the new era of cycling be led by genuine anti-dopers who crave clean racing such as Ashenden, Schenk, Kimmage etc, or will it be led by people for whom anti-doping pr is key to a marketing strategy but are happy to carry on as before with 'you pretend to ride clean and we'll pretend to test you'.
Ultimately, there are two views on Millar - either he is an opportunistic fellow-traveller, or he is a genuine revolutionary. Which it is hard to tell given his previous actions.