As soon as renewables become more profitable than fossil fuels any (personal) economic incentive politicians have to subsidise the fossil fuel industry will switch to the renewable industry. Even the most corrupt politicians you could imagine are not so hell bent on destroying the planet that they would refuse bribes from their friends in the solar industry.

The real political incentive behind fossil fuel subsidy comes down to technology and economics. The reality is that every nation is dependent on oil and gas and without them their economies would be destroyed. The real reason politicians fear a real push towards cleaner energy is that it will increase energy prices enough to trigger nationwide riots and protests.

You are correct but if we can get to the point that economics drive green energy the political opponents will have trouble stopping it.

There is a tipping point in there that we could be prevented from hitting, but I really don't think that will happen.