Well we don't know whether there was what actually amounts to collusion, but assuming there was it might have been required to break Amazon's leverage over the

Well we don't know whether there was what actually amounts to collusion, but assuming there was it might have been required to break Amazon's leverage over the bookseller which was artificially depressing prices. That wouldn't make it less illegal, but it would be a reasons why it was necessary to restore the market as a pricing mechanism.