Hydra said it was waiting to be asked to take over the world.
I took it as less "waiting to be asked" and more "waiting until people found it acceptable for government to "do more" in the name of protection."
Which, really, you could take as mirroring present-day, real-world, politics and situations where a lot of people are okay with various types of government intrusions because, "I'm doing nothing wrong."
Sixty to seventy years ago Americans may have had a lot of problems with government being able to listen in to their phone-calls, read their correspondence with others and whatever other ways you want to adapt today's USA PATRIOT Act policies and other things going on into a 1940s setting. Especially once a more "peaceful time" came in the baby-boom era after World War II where few threats were seen by Americans.
So in the Marvel Universe Hydra tried to take over the world but were met with resistance by people willing to fight for their freedom and not wanting to be ruled by single super-power with goals of weeding out undesired segments of the population.
Flash-forward to today (both in the MCU universe and our own) where we're bombarded almost constantly by terrorist threats and whenever one of these things happen or almost happen there's a lot of question on what government is doing for us in order to keep us safe. People become more and more willing to give up freedoms and convenience in the name of feeling safe.
People gripe about pat-downs and taking off their shoes at the airport but many tolerate it because it's keeping us safe since 13 years ago a handful of people managed to hijack four airplanes pretty much for the first-time ever in American skies. One guy tries to, and fails, to detonate a crude bomb made in his shoes, so we're okay with our shoes being "inspected" to make sure that's not tried again.
Some of the things people have accepted in the name of "security" in the last 14-15 years has all stemmed from a single, albeit very successful, terrorist attack. People tend to WANT government to step-in and do more to "protect us" and many are okay with it because they don't feel they have anything to fear so long as they're doing nothing wrong. Sort of forgetting what the whole "freedom" thing means.
This brings us to the MCU where inside of a couple of years there's been numerous large-scale attacks in cities (and small desert towns) due to corrupt business practices and foreign terrorists all culminating into a very large-scale attack by aliens on New York City.
So, Americans in the MCU -like Americans in president-day real world- want their government to do more to keep us safe. Enter: Hydra and Project Insight. Where the opportunity has finally presented itself where people are willing to give up their freedoms in order to feel safe. If this means launching three massive, flying, battleships that can kill anyone at anytime for whatever reason those controlling things see fit, so be it. I have nothing to worry about, I'm doing nothing wrong.
But, as the movie shows us the thing to worry about is the ones controlling the things supposedly protecting us. We *think* we're doing nothing wrong but what if what were doing is wrong to the guy with his finger on the trigger? I talk on my phone, send out my email, live my life but what if the government thinks I'm stepping over a line and need to be dealt with. (Which in the real world may mean a talking to, a legal hassle and my name on a no-fly list dependent on the level of threat they think I possess.)
In the MCU, Hydra is in control of the Insight Helicarriers and they see anyone who is not part of their ranks or sympathetic to their causes as a threat, hence their plans to wipe out nearly a million people the moment the ships had contact with the satellite network. And by that point the people of the world will see the problem with giving so much power to their government (or an organization working for the government) but by that point it's too late. Which also translates into present-day politics given that it's easier to give the government control than it is to get it back.
Really, a lot of nice parallels in the movie between the events going on in the MCU and the real world. For them, though, it's aliens and hard-core Nazi groups. For us it's people who *might* one day try and to blow up a plane by setting his underwear on fire.