USAID funding played a large role in the impeachment attempts in 2019. It's feasible that this corrupt organization was just not well on the radar during his first term. But, their deep involvement in trying to impeach Trump has brought it fully to his attention. There has definitely been something that has triggered the immediate ire of the new Trump administration. It's plausible that he has known about their role in the impeachment proceedings, and other psyops, and has kept that information somewhat private during the election campaign as it would only be seen as fodder to smear him and supporters as "conspiracy theorists". USAID is a thoroughly corrupt entity that is effectively totally devoted to pushing a progressive agenda through propaganda within and without the US. But, it's also somewhat of a limited hangout. What they don't touch will be telling. Are they going to look into the DoD at all? That's the biggest fish in the pond by far, and well known for corruption and waste of billions, if not trillions of dollars.