Yglesias' argument isn't really valid. He'd identified that companys weren't operating to pay dividends and faced high profit taxes. Fair enough. But there are an infinite number of reasons not to do anything. I could equally observe that companies weren't being operated to bridge the psychic gap between the mundane and the divine and that has equal logical power.
That sort of topic requires an active argument of the form "this is why they did that". IE, identifying how Bell's owners and operators were profiting from the work. It probably wasn't by running skunkworks and research labs.
And, carthago delenda est, the big change in the US has been the transition to a service economy and financialisation. Since research isn't likely to help that sort of economy but is in an industrial economy this change seems like an obvious candidate for why it got rolled back. Doing research while trying to be a cutting edge producer makes sense.