This is after Apple pulled its ads from Twitter. Apple is (was) the biggest payer of ads on Twitter. I was reading something like $50 million. This is just a retaliation move and I see it failing.

I'm reading he's also going after Apple's 30% pay cut on app store purchases. 

Didn't Epic already try that and fail?

They did, but Elon as an individual is substantially bigger with more resources available than Epic the business entity lol.

Musk has shown to be rather incompetent when it comes to running Twitter as all his changes are making the site lose even more money as many advertisers have pulled out of the site. Though, I guess it would be his lawyers doing the work and not him. 

Plus, I'm sure MS would appreciate any additional allies as they're looking to get into the mobile storefront space. 

It is true that the App Store and Google Play Store are very closed off. But if they are forced to open them up, what about video game consoles? They are just as closed off. Windows is the only place I see being safe as it is rather open and had many stores available - Steam, Windows Store, Epic Games Store, etc. 

This. Apple pulled their ads like dozens of other companies (50 of the top 100 advertisers) and Musk went on a tantrum and started bitching about something else entirely (the 30% cut). Epic was kicked off the app store for trying to create a side store to circumvent Apple's store cut, Epic sued, lost and solidified App Stores right to charge 30%.

Musk will lose because he's a fucking idiot and courts will just refer to the decision in the Epic vs Apple court case.

Basically, Apple has the right to charge 30% on their own store (what Musk is whining about) but do they have the right to block all sideload stores (what Epic wants) and what the EC will likely eventually investigate and what Microsoft wants too. Nobody is mad at Apple's right to charge 30% on their own store but they want the option of allowing a sideload store which circumvents the 30%.

Well, in fairness, most of Musk's wealth is tied up in stocks, Tesla/SpaceX are heavily helped by Government subsidies too and honestly, I think Tesla is incredibly overvalued but that's a different conversation entirely. Remember that Epic is largely financially backed by Tencent as well who are massive. Nevertheless, both Musk and Epic are nothing compared to the juggernaut that is Apple, Lol.

The issue is that the court case was already decided, unlikely that anyone will waste the time and effort and will just instead refer to the decision in Epic vs Apple, which Epic lost and caused a double down on Apple's right to charge 30%. It depends on what exactly Musk's complaint will be, if it's that Apple pulled advertising, he'd be laughed out of court, if it is that Apple charges 30%, he'll be slapped down.

As I see it, he needs to be more specific, the side loading of stores is an entirely different issue to Apple charging 30%, it is fully Apple's right to charge 30% and that is the industry standard, is Musk complaining about the 30% or is he complaining that Apple doesn't allow a sideloaded stores? It looks like he's just whining about the 30% cut on iOS.

Microsoft doesn't care about the 30% iOS cut, nor does EC, what they want to investigate is if it's in Apple's right to block sideloaded stores entirely which circumvent the 30% cut, like, I'm 99% sure that Microsoft would remain on iOS with the 30% cut even if it was eventually ruled to allow sideloaded stores on iOS which circumvent the cut.

Microsoft only passively sided with Epic but didn't get too involved in the court case, Microsoft is (probably) smarter than to take Apple on directly, they'll likely just let things play out whilst waiting for the EC to eventually investigate Apple/Google and then bring the receipts, they'll let a regulatory body break things open rather than attempt it themselves.