EPA has never banned small trucks. This is from consistent misinformation that shifts blame from car manufacturers to the government.
EPA made a scaled plan that required improvements to emissions from smaller trucks first, then larger trucks over the years.
Car manufacturers chose to abuse that flexibility by simply not making smaller trucks, instead of making ones that meet the standards, which is why trucks have steadily inflated in size in the US as they make whatever the next unregulated size class is that year.
You can of course partially blame EPA for not having the foresight to predict that would happen - but they also make regulations under pressure from politicians and lobbyists who are themselves influenced by car manufacturers.