Banks raise $56 billion...lightbulb anyone?

According to a recent New York Times article, the United States' largest banks, the same banks that a month ago had no money, have raised an estimated $56 billion over the past two weeks, as instructed by the government.
This all resulted from the government's recent "Stress Test", an evaluation that rates a bank's financial condition and whether or not they need to take action to stay afloat. Basically, it measures the amount of bad debt and unpaid loans that banks have and cannot collect from, followed by whether they have the current cash/capital to deal with those losses, and if they don't (and thus fail the Stress Test), the government calculates a certain amount these banks have to raise in order to be able to cope with their losses.

My question is, how could it possibly have been this easy for the 10 banks who failed the Stress Test to raise as much money as they did and suddenly be prepared for another financial
crisis? **

All these banks did was, in simple terms, sell a ton of stocks to the public, forking over certain percentages of their company ownership to investors.
We're all taught in basic business courses that any business, banks or otherwise, need a certain amount of cash/capital within the system at all times in case of emergencies (the rest can be invested in stocks, equipment, or other productive assets).

How on earth could it not have dawned on these banks, while the sub-prime mortgage crisis took flight two years ago, that they should probably buckle down, swallow their pride and prepare for the worst by selling so all this stock back then?

Obviously, trust is an issue here and probably the reason we've arrived to the state we are in right now. If I am desperately trying to sell my house and am struggling to do so, I'm not about to fork over my savings back into stocks.
My only sticking point is, with all the bailouts we've had, with all the major companies that in the past two years have invested hundreds of millions in the stock market to encourage the public to do the same, why does this only work now? Because the government said so? I'm not buying it.

I feel a lot more could have been done way earlier, but credit to the Obama administration and the Treasury Department (not being politically biased here, just realistic) for finally getting something done, hopefully the Better Times (because they are by no means good) keep rolling.


** It's worth noting that of the $56 billion raised, only $48 billion was raised by banks who failed the Stress Test. The other $8 billion was raised by nine other banks voluntarily as a strategic move.