It also has to do with flexibility and survivability too, it wasn't just so the USAF and Navy could get a share of the nuke funding pie and prestige though that was a secondary benefit. Bombers provide the maximum flexibility in launching and targeting while the number and dispersal of our ICBM's provide an insurmountable targeting problem. Every one of our ICBM's has to be individually targeted even with nukes in order to destroy them, an almost impossible task given the fact we have over 400 of them.
I doubt the SSBN's are the only ones funded, especially when it would mean putting all our nuke 'eggs' in just a few baskets. While the Navy likes to brag about the survivability of the SSBN's there are only a handful that are deployed at one time, it is a lot harder to destroy 400 targets than 4-6. No matter how stealthy subs are the sheer numbers of ICBM's ensures their deterrent value even if we reduce our current force by half or more.
I have seen estimates that the new SSBN's could eat a massive amount of the Navy's shipbuilding budget, a big reason Congress has pushed the 'National Sea-Based Deterrence Fund' mentioned in the article make it separate from the rest of Navy's budget.