So what your saying is they threw thousands of soldiers at the Mojave for a minor gain? BULL. If the Mojave's resources were hardly of any consequence then the NCR wouldn't have bothered fighting over it
So either
A: Its significant and the NCR can't risk losing access to it=House has Leverage
or
B: Its insignificant in which case its not worth throwing away anymore lives.
The fact is its stated in game the NCR needs the resources of the Mojave. Chief Hanlon mentions that they dried up all the lakes back east. And for five years the Hoover Dam has been providing the NCR with an abundant amount of electricity you try and take that luxury away you'll have riots from angry citizens and businessmen who've suddenly lost access to that, THAT is bad business and the cost of another war after the last disaster would be even worse for business.
Its also stressed again and again the NCR is over extended and you've just given a long list of reasons why the warhawks would be throne out of power and replaced with more diplomatic leaders.
*What mutant armies? the Master was defeated long before the NCR even existed.
The NCR is very good at pushing around small weak groups like The Khans. Or overwhelming an actively attacking enemy like the Brotherhood of Steel. The problem is the Khans and the Brotherhood never had leverage over them. House does. The Brotherhood of Steel as actively attacking them they didn't have much of a choice in that fight. House just wants them out of the Mojave they can still buy power and water from him at a cost which undoubtedly would be far lower then the cost in engaging in another costly war.
The Legion threatened to invade the NCR, so they had to be fought before they could grab a power base in Vegas. The Brotherhood of Steel was actively trying to take technology out of NCR hands, they had to be fought.
The NCR doesn't have to fight Independent Vegas inorder to get electricity and water, it isn't a threat for invasion so they don't need to protect themselves from that. They aren't raiders like the Khans. Also I've seen nothing to indicate the NCR is remotely competent at covert operations. How would they sneak a bomb anywhere near the Lucky 38 the Security would vaporize anyone coming close to the building.
Lastly House wins the Mojave it means the Courier backed him. The NCR has no counter for the Courier and for a historical reference plenty of countries fought and won wars of independence and when the dust settled turned around and engaged in peaceful trade with the former mother country because it was economically beneficial.
They aren't a 21st century country where if you turn off the power, civilization implodes, they are just recently going through an industrial revolution, it's not like they've forgotten how to make things like candles or lamps or run a business without electricity in five years, most of the advlts were probably doing that for most of their lives. They've endured a lot, lot worse. If they didn't rise up when the Brotherhood was on the march, do you really think they will rise up just because they only have electricity for a couple hours a day? Hell, even steam power is just being reintroduced. Their need for electricity is growing, but it does not seem to be at a critical level yet.
You're missing the point entirely. Securing resources you're going to need in the future is not an unwise move, but saying that House's control of the Dam is like the Sword of Damocles from day one, is just frankly untrue. Your scenario makes sense 50 years down the road, but not in the short term. It is certainly in the interest of the NCR to control the dam in the long-term, and I would strongly support that course of action personally, but they'll survive short-term while they plan their next move.
You do realize that everybody around them used to be much, much stronger than them, hell, the Khans kidnapped
the President's daughter and they had to fight their way from being a dusty little town beseiged by raiders into a modern nation-state, all of whom had the greatest kind of leverage, being able to physically wipe them off the map. And I think that the cost of kowtowing to a naked attempt at blackmail by a delusional warlord who's talking about building bases on the moon is a far greater price to any nation than any monetary value. Even viewing this issue through that frame of mind, in this case, the price of peace is infinitely greater than the price of war. If House is not dealt with as soon as possible, he will do nothing but drain wealth from the NCR like a common parasite, which is as great a threat as any of the NCR's foes, but in a different way. The threat of the Enclave, BoS, etc. is military, House's threat is economic.
That dosen't mean they won't be back, because given their history, the chances are good that they will. And as their need for electricty grows, the less inclined (if that's actually possible) the NCR leadership with or without Kimball will be willing to leave a
hostile foreign power holding the keys to their economic livelihood. Some will argue that as soon as the war with the BoS is finished, the NCR should turn its attention to reclaiming the Mojave before they become dependant on an enemy, and it's not an unconvincing argument, either. There's a good chance that those voices will be heard. Will it be costly if it comes down to that? Of course. Will the public get behind the war? That's a mystery,but I think a sizable portion will relent when the full effects of House's "peace" begin to hit home. They might not support it, but they won't shed a tear over a robber baron getting some old-fashioned payback. In the end, this is a rough neighborhood, and such sacrifices are necessary to prevent House from gaining the kind of power you want him to have of the NCR.
I wasn't saying the NCR should engage in that sort of business, but one of the families did manage to sneak in a small arsenal from a secret patron once before, and in Vegas, you luck can change just like that. I think it would be a rather befitting end to a man who came to power by betraying others to be betrayed himself, don't you?