Did planets form because of electromagnetism?

For myriad reasons, the answer to this is an emphatic yes.

Gravity may attract particles towards each other, but the force that actually causes them to interact with each other is almost entirely electromagnetism. The collisions of grains of cosmic dust are caused by electromagnetic fields interacting with each other. As is the gradual loss of kinetic energy -- the friction -- that allows some amount of potential energy to get converted to heat, allowing the particles to slow down and, as you described it, clump.

Absent electromagnetism, the actual particle nuclei would need to directly hit each other to cause an interaction via the nuclear forces, which is VERY improbable in the vastness of space. Improbable doesn't mean it wouldn't happen, but in this case it does mean the universe is way too big and young. Without electromagnetic interactions, particles just form orbits. Which again, that's what a "dark matter halo" is. It's all the dark matter stuff orbitting around a galaxy's center of mass because it doesn't get easily trapped in the center. It's all the dark matter in a gravitational system constantly whizzing back and forth across the center of mass since there's no electromagnetic force to rob them of the potential or kinetic energy and stop them from heading back out.

And, conveniently, these halos are just what our observations seem to indicate dark matter is doing in a typical galaxy. The observations and theory align well