It's a bit weird to size such large part of the Fallout land with entrepreneur skills that requires bulldozers, lifting-cranes and more.

If there was a quest in the sanctuary and the group leader would offer something for building a fence around the whole settlement, it would have better proportion. But the settlers are just tools. You can in a minute destroy all their beds with your magic wand and without troubling their minds.

There are no rival settlements, you are just a bazooka entrepreneur that arives 200 years from the past and quickly erects cities all around with a magic wand.

In the old days houses looked much more individual, because each family usually built its own and could decorate with their own beliefs. It's only nowadays where individuals only find room to build their own on facebook that's got lots of space, while their settlements is sized by a few entrepreneurs, why everything looks so much more alike, since the few entrepreneur-brains only got so much capacity to decorate. If stuff in the modern settlements didn't have signs and addresses, it would be impossible to navigate, since most built look alike.

Just how do you explain entrepreneur powers in a post-apocalyptic world, when you just arived 200 years from the past and haven't got a clue yet to anything?

Because it's a game?

Not really! Because they could allow for example you to build only 1 settlement completely creative, and the rest by quest instructions because why should the player be so ambitious as to build others settlements, besides other settlers have their own ideas; and they could let the construction take more time - some animation involving helpers to contruct. Etc

There are raiders that attack, moreso if your defense is lower than food + water totals.... they see a rich (in food and water, the currency of the wasteland) community with poor defenses, and they try to take it. They're not exactly rival ~settlements~ because most settlements are small and if they are peaceful they are likely trying to hang on to what they got.

As for why ~you~ get to design everything, well, the player is basically a god to these people. They eek out a living as dirt farmers and you come blazing into town with power armor and mini-guns and decimate all foes who oppose you and then have the initiative and ambition to start ordering people to build houses here and here, and do this and that, and people follow you because you're the leader / despot.

Not sure what you mean but they're all uneducated on the raggedy edge of survival and never knew any better. Most have little to no math skills, literacy, hope or ambition. You at least have some basic knowledge about how the world used to work not only in engineering but social and politically. The settlement perks revolve around this idea or you being some kind of politician. As much as the character has to learn about the new world they bring knowledge from the old one that has been lost much like the renaissance rediscovering math and engineering of the Romans.

That's what seems weird! Not that it isn't playable like other construction games. But it's more like the Fallout Entrepreneur.

Perhaps it could start with an entrepreneur quest like one of the settlers comes and explains that he's seen all these bulldozers and building machines from older times and that he'll probably be able to get some power ...

Who built and how was New Vegas safe heaven built by the way?

Seem like the settlement is actually the first evil turn the player takes in game! Because as a child you'd expect your parent's protection and immediately disregard them when they failed to do so! And after the first deathclaw incident you get the opportunity to either go back to sanctuary to start settling or to continue after the child. Starting to build a settlement is a time consuming and a giant disregard for the kid's well-being. Pitty the game fails to see it. But if you had to explain it to the kid, what took you so long, then the truth would come out.