One side point on the corporate legal issue, which I believe you have completely wrong: the new company is liable for claims made against the old company it acquired. Now, they do have the option of then filing a lawsuit against the shareholders that sold that company, if the liabilities were deceptively hidden.

But this is one of the real risks of a company merger: acquiring a company with unexpected liabilities from the past, and there's often terms in the company merger agreement, to allow for redress against the sellers in such cases or to hold back part of the payment for some time, to make sure no such hidden liabilities emerge.