It sounds like you have no idea what a free market actually is because monopolies can and do exist in them.

Say a chair-maker started making chairs in 1900. Over the years, he built up huge factories and was thus able to lower the cost of producing chairs to practically nothing since instead of paying people to make them by hand he can just have a machine spit out hundreds of them.

Now, in 2018, you want to start making chairs. The problem is that it is expensive as fuck for you to make chairs since you're starting with nothing and can't afford the big machines. Nobody buys your chairs because they cost so much more. Now, the other chair maker didn't forbid you from selling chairs. You just can't compete because they're already so big. You starve and die.

There is no government intervention or regulation in this scenario yet a monopoly exists. So if we're insistent that the other chair-maker does not have a monopoly and therefore don't interfere with the free market, you need to find some other way to compete. The only way to do that is to differentiate your chairs from the other chair-maker's.

So you go to a design school and beg designers to give you their chair ideas instead of the other chair-maker. They ask you why they would ever do that so you tell them they can keep the money from those chairs, you just really need something to get people in your store. Since they're broke and about to go homeless anyway, they agree.

This is literally what's happening with the Epic Store. Yes exclusivity sucks but Steam is very close to being a monopoly simply because no developer has any reason to move their games off the store. Epic is doing what they can to break into the market and again – exclusivity fucking sucks, but I support their attempt even though I have no intention of participating.