I won't make it an argument, but I'll share what I know and see if you see things differently. You probably won't, but I'm inclined to say it anyway :-)
First, to clear some things up, I'll avoid conflating traditional enterprise servers and hosted servers with the on-demand, pay-as-you-use cloud model. The later is what I mean by "Cloud", not just hosted servers.
To my knowledge Red Hat only holds a lead in server OS installations with paid support, and that's almost all in the former model (non-cloud, for me). Incidentally that's also the stat you'll see when companies publish reports about Linux's market share in general - they often just look at who's buying Linux. It's hard to get a real picture of what people actually use when you include unpaid Linux usage (which is most Linux usage), but the best data I know of is created by scanning web hosts, and suggest that Linux server run in order Debian, Ubuntu, CentOS and RedHat:
http://w3techs.com/technologies/details/os-linux/all/all
Red Hat's sudden obsession with OpenStack in the last 12 months, the move to take over CentOS and the purchase of InkTank are reflections that Red Hat are struggling to get in that game and are prepared to spend big to do so.
Why are they struggling so hard? Because they're frightened. The steady, "we want everything to stay the same for 10 years" model they've been serving so well is seriously threatened and they need to be in the new market to continue their success. Businesses love the idea of the cloud (if not yet the reality). Read what companies say about the cloud - they'll talk about it in terms of flexibility, and opportunity, but what they really love is that it means that you can offload the genuinely generic work of IT infrastructure management. This reduces the reliance on staff and consultancy costs, which are the most expensive aspect of corporate IT (hint, want to stay employed, get with the program, fast!). It also means that whether you're using Red Hat or Ubuntu, you get to negotiate the fee for OS level support via a behemoth like HP, Amazon, Microsoft or Google, or if you're a huge company with a private cloud, you centralise all that and do it in bulk. The same goes for the physical space for hosting.
Now Amazon were an existing Red Hat customer and so their servers were already running that when they started on this public cloud adventure - which afterall was a clever way to reuse their existing investment in infrastructure and personnel outside peak load time. That's not a big win for Red Hat, but there's growth of their existing business for sure (who knows what kind of deal Amazon got from them?). Still, the utilisation of that cloud is the bigger chunk of new business there, and it's Ubuntu winning the majority of it.
Now spread out to the nascent cloud market as a whole, sure Amazon are a huge public cloud with the bulk of utilisation, but there are many others, new ones all the time. Additionally and many, many private clouds that are being created those are the opportunities for new revenue in the hosting market. Almost all of them are going with OpenStack and 55% of OpenStack deployments are Ubuntu right now (I've seen Red Hat running at less than 1/10th of that business. I'd expect Red Hat to increase that number a lot in the next couple of years (they'll convert some existing customers for sure), but don't be fooled by the recent, aggressive press releases from Red Hat - they're fighting to get a foothold in this market, not controlling it by any means.