Why is that so surprising? It is hard even for technically-inclined users, let alone regular ones.
To me, almost anything that can be completed in a fixed amount of time with high probability isn't hard; it's tedious at most. But if it can be completed within one hour it's not even tedious, it's (IMO) 'easy'.
For something to be 'hard', there should be a reasonable chance of failure with associated non-trivial costs.
Any single part of a computer is a non-trivial cost if broken, and it's not too difficult to imagine the situations where that might happen: bending a pin on a CPU, giving a static shock to a component, misapplying thermal paste.
Even for enthusiasts, this is a task they do perhaps every 3 years, and every time with different components.
Pins are in the socket now and very small, pretty much impossible to bend without negligence. Thermal paste is also usually pre-applied to the stock cooler, and you won't need to apply your own unless you're using an aftermarket cooler and overclocking.
Static shock is probably the only real concern but honestly I've built at least 20 PCs, at least 5 while wearing socks on a carpet. I've just never seen it be an issue or even met someone in real life who shocked hardware.
Parts are also much more durable than you'd initially believe. I competed in a PC building race (weird, right?) and most builds took 2 minutes or less (some stuff was pre-assembled). Hardware was slammed into motherboards as fast as possible, clumsily dropped on the floor, no regard for static. No attendee had any hardware issues.
> Even for enthusiasts, this is a task they do perhaps every 3 years, and every time with different components.
Nah, for those of us who love it, we'll gladly build your PC for free (for friends) if you buy the parts, I'll even double check the build first. Though I do try to haggle a six pack of beer out of the deal.
Example of modern pins:
https://www.techpowerup.com/reviews/MSI/Z170A_GAMING_M7/imag...
I did this back in highschool as well. We actually did have a team one year who broke a computer but that's because they were bleeding all over everything. There's a surprising amount of blood in these competitions when you're racing to put components into a completely unknown case with sharp edges all over.
It takes willful ignorance and disregard for the simple instructions included with each component to even have a chance at breaking the expensive things.
Can confirm, got a little lazy and put spare components together into a working system on the carpet this past weekend. Everything still works well enough. :)