Social Media is not the only problem, it’s far worse than that and you will not solve it leaving social media. Your employers get all the information about you from what is called ‘data brokers’ which are the ones who buy the data collected by all the apps that you install in your phone and sell it to everyone interested, not only companies trying to sell you something, but also employers like the case you posted and also state agencies, who dodge in this way breaking the law by spying you. That’s the big business of data collection. Here an investigation made by german journalists How data brokers sell our location data
Yeah, the solution to apps selling your data is using only free software, the only problem that still remains is that your mobile network provider also sells your location data.