Sentence Correction (SC) | Re: In the late 1960s, the rising number of American casualties in Vietnam

What suggested to the US that the Vietnam Project was futile were the increasing number of casualties by the late 60's and the 1968 Tet offensive by the Vietcong.
The rising number also indicates that the losses were ongoing and continuing with no end in sight.

If we use the past perfect, then these incidents must have taken place and ended in the deeper past than the realization by the US. But the incidents and the realization by the US seem to have happened concurrently. So, why do we need