Let's take reality, RedHat is still a small player compared to Amazon, Microsoft or Google. They don't have the bandwidth to compete on all the additional hosted services offerings. By partnering with IBM, they get access to IBMs entire suite of enterprise customers and hosted products, making them a serious competitor to the 3 big players instead of being a "me too, cloud". They could make it big together, looking optimistically. But it's on IBM to not screw this up.
I think a lot of readers probably don't understand what that line means. Even if the C-suite at RedHat did not want to do this, they have no choice. Shareholders can riot and oust you(executives) for not taking what they consider to be the "best deal"(and this is one heck of a deal). Long story short, even if you don't want to sell - once the price is high enough, the shareholders will force you.
.. they probably though the price right now is better than what they would get in 5 years.
That $120 was really high for redhat, who just crossed the $100/share price last year. (unless you count year 2000/dotcom-IPO-madness) RHT's market cap was previously $20B.
That's not weird. It's a bit much as these things go, but 20-30% over the share price would not raise any eyebrows.