The "This genius person's plan failed because they didn't account for human emotions!" thing is often just a writer's excuse to have their supposedly smart character acting stupid
If you couldn't tell already, this is about The Boys, and Sister Sage to be specific. So spoilers about that.
Now, this trope can be done really well, but usually it isn't. You don't need to be a super empath in order to understand how people act.
You can look at, for example, real life psychopaths. They lack empathy for others, and experience shallow emotions. Yet they can still be very effective and manipulating people. It'd be strange if a genius wasn't aware that people often act in irrational or unpredictable ways.
I've been seeing a lot of people saying that about Sister Sage in the last episode, but I don't think it makes her seem like she misunderstood human emotions, it makes her look like a moron.
Her plan was to separate Homelander and Soldier Boy using Homelander's past relationship with Stormfront. The next step was to have Soldier Boy take out Bombsight (this step on its own was also very stupid, Bombsight was weaker, but not significantly weaker than SB, what would she do if Bombsight got lucky and won the fight?). And then her genius checkmate move was to have... Soldier Boy not give Homelander the V1?
Let's assume that the probability of SB giving Homelander the V1 was very small. Like 5%. This is still a fucking stupid move, because her plan had a single point of failure. All it took for everything to go completely wrong was for that single 5% probability event to happen. True geniuses introduce redundancy into their plans, which means even if one thing doesn't go as they wanted, their whole plan doesn't go crumbling down. Sister Sage missed the how-to-make-a-genius-plan 101 class, apparently.
Anyways, this is just a trope I really hate, and giving a recent example for it.