I don't think it's a particularly different timescale to swap from ICE to EV than to drastically reduce car dependence. What makes you think there's a big difference to where swapping to electric cars is easier than avoiding cars?
Credible reduction in car dependence needs well connected fast passenger rail networks, and changing urban sprawl to something denser with more local amenities.
The first one is a major infrastructure project, the latter is largely unpopular with the people already living there (and Republicans react to the concept of 15-minute cities like it was a gulag).
Infrastructure is still built as if it was business as usual, so can easily get blocked and delayed by decades on budgeting, bidding, consultations, NIMBYs, environmental surveys, etc.
OTOH we've already got EVs, we have already been building infrastructure for them, and it's a smaller change more acceptable to people.