I think they expected more from their descendants.
They never envisioned such a needy, helpless electorate
They also over estimated the urge to preserve liberty and freedom at the cost of regular revolution.
The fact is the framers created a strong national gubmint where there was none. They made much more than a stronger confederation. They obliterated the confederation and replaced it with a national gubmint set up like a rube goldberg machine, and that was supposed to guard against tyranny?
I think they knew the human weaknesses involved. I think they knew the Spirit of 76 was a rare--almost sacred thing. I think they just went too far, gave the national gubmint too much power, and included far too much superfluous language that was unnecessary and haunts us to this day. I'd throw out the entire preamble. No good comes from it--only mischief.
I don't think they did it on purpose, although Patrick Henry famously "smelled a rat." I think perhaps Jefferson needed to be there. He could have done some good. His extremism could have been put to good use.
I'm at the point where, when I hear conservative commentators saying people should read The Federalist Papers, I just roll my eyes. They inform us about the intent of the framers, and have great value, but they are also a monument to the bizarre naiivete they had, an inexplicable blind spot to the failings of the document they produced. Maybe they just fell in love with their own work. It happens.
For me, I think I'm better off accepting it as a failure, and moving on intellectually. No use beating my head against a wall about it. They failed. We failed. Done is done. The verdict is most definitely in as far as I'm concerned. That's why conservatism fails in practice--it's an impossible task to undo what's been done. Sorry for the long reply.