Robo-signing didn't force unqualified borrowers to borrow.
Robo-signing didn't force unqualified borrowers to default.
Robo-signing didn't cause the crisis.
This is called 'Remove Blocking Cause', for example a dam holds back water, and if you remove the dam you flood the village.
Your logic is the equivalent of saying that removing the dam did not flood the village when we all can see the cause and effect.
Robo-signing was part of the problem that cause the real estate meltdown, but obviously it was not just that.
The banks needed more mortgages so they could sell more derivative contracts called MBSes, SIVs and CDOs. So they bought anything that was available from smaller lenders, like local banks. Local banks could make the stupidest and most irresponsible loans and then sell it to the Too Big To Fail Banks and not take any losses from the bad loans.
The security rating agencies like Moodies were coming up with nonsense reasons to justify giving these contracts AAA ratings, but the basic reason was that the Big Bank could take the security somewhere else and get it rated there if Moodies panned it with an accurate evaluation, and on top of all that the people giving the ratings really didnt understand what the securities were nor the complex algorithm everyone was using to evaluate the reliability of the security. (The chinese guy who wrote it said that it was not supposed to be used in real life and was only an abstract academic exercise. The SEC was just assuming that everyone was being honest and doing their jobs because they didnt understand it all either and most of their employees hope to get jobs at the Big Banks anyway, so they have no incentive of busting up the Big Banks little money making con game.
So, no, robo-signing did not cause the crisis, but it certainly did contribute, since of a bank loan officer had actually read and evaluated these loans instead of just assuming that they were all good, non e of this would have happened because there would have been no bad loans for the Too Big To Fail Banks to buy and repackage.