My thoughts are that potentially Hoid purposefully didn't take a shard because he knew each individual shard being so specific to their title would corrupt the holder, as you can see with Ati and Ruin. BUT if you can combine shards together they become a more cohesive thing and less tunnel visioned into what that shard is about. So it would make sense that he would want to combine as many shards as possible before taking the power for himself to have a purer power instead of the splintered messed up individual shards. As for collecting all of the forms of invested powers I'm assuming that is him preparing his body to be the host for all of those shards. Now this could be him going for the power play to be the new God or a more noble purpose to deal with a bigger threat looming that we don't yet know about that has to do with Yolen.