The government absolutely did not sell an insurance policy before the crash. Even if you're arguing that there was a guarantee that the banks would be bailed out, which argument has merit, the banks didn't pay for that guarantee.
We did it for different reasons (I won't pretend I was either magnanimous or delusional enough to think my investment by itself would buoy the stock price enough to keep the companies alive) but the actual actions are the same.
Edit: technically both the government and I bought during the crash rather than after; my ROI wishes I'd been better at calling the bottom, but that's life.
The government had essentially given the finance industry an insurance policy before the crash that paid off during the crash. And you are right, they didn't have to pay for it in money, perhaps its possible to argue that they paid for it in regulation. If the firms had had to buy such a policy on the open market what would the price have been?
(2) Even if it had, "it worked out" isn't a good justification for gambling with taxpayer money.