A MBAir is not a gaming computer. I would not expect games to run very well on a MBAir. Make sure to completely close or rather Quit all other apps when running the Sims 4.
You also neglected to mention the exact model of this Mac and version of macOS used. This is very important information. You can run the third party app EtreCheck and post the complete report here so we can examine it for clues. This report will give us that information as well as lots of other useful information pertaining to system performance and the crashes.
Are you sure your MBAir meets or exceeds the Recommended System Requirements? If you are running an Apple Silicon M-series Mac, then is this game supported on it.....that is, does the system requirements specifically mention M-series Macs and your version of macOS? You should check the Sims 4 game forums to see whether your exact model laptop and OS are supported and how well it may be supported & perform.