What is it about TS4 that makes a computer run so hot?

Yesterday I played Sims 4 longer than I usually do. I have a gaming laptop that heats up really badly after about an hour of playing and I use a cooling pad. After playing about 3 hours yesterday I noticed that my laptop smelled like something was burning. I immediately stopped playing and closed the laptop.
Today I've used my laptop already and it seems fine. I hope it's not going to break up when I will play Sims later today. I'm definitely not going to play more than 1-1,5 hours this time.