why is multi-tabling so hard compared to single table focus

I keep seeing folks say you gotta play more than one table if you’re trying to be serious about poker, especially online. Every time I add a second or third table, my brain just feels scattered, like I’m never giving the same attention to spots as I would on a single. Even after a few weeks trying to up my volume, I end up misclicking or timing out on hands I’d never miss one-on-one. My stats tank and I start leaking chips with random bad decisions I catch later in review.

I know it’s a learning curve thing and some players seem to handle six or more like it’s nothing. Is this just a brain speed issue or something else I’m missing? Do you get used to it, or is there a point where you have to accept single table is just more intentional and better for some playstyles? Wondering if there’s certain drills or routines you guys use to stay sharp once the tables start piling up.