Pileup due to snow storm - GIF

[desbromilow]

so what is the main issue here? - excessive speed for visibility? loss of traction leading to reduced braking?

I know it's easy to blame idiot drivers, but for someone who never has snow in their area, I am curious as to what people SHOULD be doing when driving in it... I see people refer to snow chains, but I can't imagine they are for high speed driving
Do the main roads people have different speed limits for snowy conditions compared to sunny dry conditions?