"Destroy capital" is unavoidably speculative, I think. I'm not sure it's the most useful frame. No need to be abstract if we're referring primarily to a few large companies/conglomerates.
Instagram, Whatsapp, Youtube, Android, Doubleclick, etc.. Those acquisitions are undoubtedly a major part of how Google & FB got to here... and here is a good place for shareholders. IMO, it's hard to argue management destroyed value, but we don't ever know alternate realities.
Either way, I think there's a strong case that "competition for monopoly" is the key dynamic here. A business similar to adwords-google but with only 1% of the market share is worth way less than 1% of adwords-google. Think of Yahoo/MSFT's attempts at adwords' runner ups. How much is reddit worth, relative to FB? There are lots of examples. Even if the market does have multiple contenders, the power curve tends to be mighty in modern, software-centric economics.
For a variety of reasons, strong pressure to consolidate appears to be the case often. Whatever those reasons, this creates/describes a strong incentive to consolidate. We know empirically that consolidation happened, and acquisitions played a role. Consolidation also happened in cases where acquisitions didn't play a major/obvious role.
Tax laws are one of those reasons, but not the only ones. There's low interest rates, the laws of other countries, the business cycles, financial markets, etc. It's financial markets that have the operative say on capital creation vs destruction. They value FB highly, and have usually seem pleased with M&A in terms of demand for the stock.
There are also "natural" reasons for M&A, and consolidation more broadly. Software is cheap to replicate/scale and is often winner-take-most. Media is similar. Ad markets (and marketplaces generally) exhibit network effects. Networks (like social networks) exhibit network effects.
IMO the whole theoretical/legal framework of antitrust is quite bougus, in 2021. Monopoly isn't just about pricing power, and whatever else ancient economists observed in previous centuries.