Buys him time, the audit was necessary otherwise bonds/loans became due or a finance line would be withdrawn. By switching to KPMG he bought himself some time, probably to hide some of the assets they would likely try to seize, so that once he has done his 18 months he can go back to his multiple homes and yachts and live comfortably.

KPMG in german stands for Keiner Prueft Mehr Genau: nobody checks thoroughly anymore. I guess he just thought they would provide the desired result...

At some point you start believing your own lies so he probably thought everything would be fine and the markets would be calmed with another auditor confirming the results.

This exactly. Allegations of fraud had also bubbled up several times in the past and he was able to take care of them. I would imagine he didn't expect this time to be any different.

Auditing is required by law.