What would you consider ambitious?

Mandate that ICE cars be 30% more fuel efficient in 2025 OR 80% by 2030?

And is it better to have ambitious goals vs realistic goals? What might the impact of society be if we put up very ambitious goals but fail them all massively, what will happen to the trust of government institutions?

P.S I have a B.Sc in Energy engineering and working on a M.Sc in a field of renewable energy and I'm very skeptical of the goal politicians make, many goals who should be fulfilled when they have long since left office.

And is it better to have ambitious goals vs realistic goals? What might the impact of society be if we put up very ambitious goals but fail them all massively, what will happen to the trust of government institutions?

this. exactly why no one trusts their governments anymore.

Personally from what I've read and seen in terms of progress by governments and manufacturers, I think it's a stretch to even entertain the notion that by 2030 the majority of cars won't still be internal combustion powered. The amount of electric vehicles on the road is certainly increasing day-to-day, but I'll just be impressed if even half the cars sold are purely electric by 2030.

Switch from horses to cars where rather abrupt, like within 10-15 years.