They clearly knew and were planning this all along. Governments always wag their finger and charge you hefty 'sin taxes' on things that they insist they dearly want to encourage you to stop doing, but then they crap their pants at the loss of all the lovely money when people do stop doing them.
They're very like credit card companies, when they piously rebuke customers for incurring high interest fees, late payment fees and over-limit fees, rather than using them 'sensibly' - when it's clear as day that they base their whole lucrative business model on their reliance on people doing just that.
I genuinely think that they're now happily leaving behind the 'carrot' approach for EVs and will soon be going full steam ahead with the 'stick' approach for ICE cars. They already double-tax fuel, as well as charging VED (and not forgetting tax on insurance premiums and the E10 petrol stealth tax), so there will also be PPM on petrol and diesel cars soon as well - probably at a higher rate than for EVs - and it will be in addition to all the current taxes, not replacing any of them.
In starting with the PPM on EVs, and the very predictable arguments that this has caused between EV and ICE owners, they've clearly deliberately gone for the divide and rule approach.