I don't know enough about the detail of what happened at Carillion to take a view yet on how culpable the government is in the collapse of the company.
From the numerous articles in the FT about this, it seems they bought other companies, took on a load of debt and were overstretched when they had some large project failures. Projects were ending without new work coming in. The FT opinion pieces say too much debt, not enough equity.
Apparently, the overreach of the company was noted by some hedge funds back in 2013. It's unlikely, in my opinion, that the company imploded quickly and I would speculate that there are a series of decisions made by banks, auditors and Carillion management that, retrospectively, made liquidation more likely. There have been profit warnings from companies like Mitie, Capita and Serco, so it's a problem across several companies taking on long-term government contracts.