I believe the ever loved by leftists North
wanted “black people” to not be counted as people at all.
The initial proposition was to have the representatives allocated to the states in proportion to the voters.
Slave states denied the vote to slaves, but wanted the representatives to be in proportion to the total number of persons. The slave power wanted represenation for the slaves to whom they denied the vote.
The compromise was to permit 3/5ths of the slave population to count toward representation. If the slave states wanted more representation than that, they could have freed their slaves.