You can. That's what a Farnsworth fusor does (there are other related designs, but that's the original, and the kind you can build in your garage).

But for complicated reasons, it just isn't efficient enough to actually produce net power output. Of course, neither is any other design right now, but magnetic confinement appears to be the more promising path forward.

Thanks for the explanation. I looked up some of those designs.

Now I'm really puzzled why no one has tried a more naive approach. I'm picturing a hollow metal sphere with a high positive charge with positive ions inside of it. Wouldn't it push them all together and with a high enough charge get them hot enough to fuse?

Counterintuitively, this setup would have zero force inside the sphere. It turns out that being closer to charge on one side of the sphere is always exactly balanced out by the more distant side's greater total charge.

Apologies if this is a stupid question but aren't they the same thing?

Nope. They are both part of the same thing - the joint electromagnetic field - and they transform into each other in different reference frames, but in a given reference frame, the electric field and magnetic field components behave quite differently.

It blew my mind when I learned how magnetism is a consequence of special relativity.