Why has it taken the work of one tax campaigner to stop online vat abuse?

Following Amazon UK reviews Chinese traders before VAT fraud clampdown, Richard Murphy of Tax Research UK asks:

First, why did it take two people  – indefatigable VAT campaigner Richard Allen and Neven Juretic of VATfraud.org – to make this happen?

Second, why did this only happen when Richard got Rob Marris of the Labour Treasury team on board?

And third, if Amazon knew of this risk why did they not act before now when the cost may have been £2 billion a  year to the UK?

If think the first is for HMRC and the Treasury to answer, the second for David Gauke MP and the third for Amazon.