Because that's actually not how the world works.
With traditional company, some consumers are paying it for a service. Apple is making 300B$ a year because a lot of people are willing to partake large amount of money in exchange for some good that they (think they) need such as a laptop or a phone. The consumers have no expectation of getting that money back later, it's a trade.
If you think Apple is a good company and will be more successful in the future, you can decide to invest it in, and you buy a share of that company to some other investor against cash.
In theory, it's possible for every single investor of Apple to make more money than what they paid for through dividends: As long as Apple keeps making products that people are willing to pay for, it will make money, and investors get a chunk of that money.
Here value is created by work happening in the entire value chain needed to produce the good. Because if you had to make your laptop yourself with a pickaxe, it would be quite inconvenient.
Also, if everyone suddenly decides to dump all their Apple stock, it will go down a lot, but not to zero, because the company as an actual intrisinc value: they have hundreds of billions of $ in cash in their war chest, have a lot of valuable physical things, and will continue to make hundreds of billions every year no matter what people on the stock market think.
Overall it's not a zero sum game, because consumers are providing an external source of cash to the investors.
Now, the more a stock is overbought, the closer it becomes to zero sum. Tesla for example, if it fails to realise the bright future that everyone is betting on, then it will get ugly as it's current stock value is disconnected from it's current intrinsinc value.
Axie is very different, the price of the token only rise because of investors (here players), there is no external source of money going in that could make everyone richer.
It's a bunch of people sitting in circle around a pile of cash with the promise that they will be able to take a random piece of the pile later on. And if you want to be able to sit with them, you first have to put cash on the pile yourself. Looking at the pile of cash getting bigger and bigger is exciting, but you will have to fight everyone else to get more than you put in.
Oh and while you are sitting there waiting for the pile to get bigger, the people that organise the event are shovelling money out.
All (most?) crypto games today are zero sum. However it's possible in the future that they may not be. I am thinking specifically about the ones that brand themselves as "metaverse". If the game in itself is interesting enough that people are engaging with it for a long time, then companies will want to start advertising in it, and if shares of that revenue are reinvested in the in-game economy and not just entirely taken by the company behind the game, that could be an example of external influx of money.