Indeed. My Uncle was involved with the installation of Samson and Goliath [0], the two yellow cranes at Harland and Wolff. Goliath was installed in 1969, and the story of the ships being swapped was told to him then.
The story told to him was that Morgan had ships ready to sail to the rescue from New York, but they ended up fog bound and delayed.
[0] https://en.m.wikipedia.org/wiki/Samson_and_Goliath_(cranes)
It doesn't involve intentially killing the people, since if the ship didn't hit an iceberg there would have been time to rescue them.
So it either all of that, or it is just an accident caused by bad technology, bad practices, incomoetence, corporate preasure ans greed and bad luck. Your pick on what you want to believe.
> Repainting, changing the interior and all that involves a shipyard.
The ships were in shipyards together after the damage to the Olympic, and major parts were swapped between them. Sure, many people would notice.
> Why not have them on route and near by the Titanic
They were meant to have ships nearby.
> how exactly do you sink a perfectly good ship?
The iceberg wasn't meant to sink it. When the ship left port, there was a large fire on board, one that had been going for days or weeks.
I'm not sure if that's the theory on how it was supposed to happen.