I have difficulty seeing the difficulty of what's happening, or I'm missing the point. I see the situation in a similar way as objects of different weights fall

I have difficulty seeing the difficulty of what's happening, or I'm missing the point. I see the situation in a similar way as objects of different weights falling at the same rate--if we think of the object as composed of many independent particles which are affected. For the case of the water in the pail, each water 'particle' is moving linearly until it bumps into the wall of the pail which diverts it toward the center of the pail. This action causes accumulation near the wall. The same could be done without gravity and water would start as a disk perpendicular to a cylindrical wall then become a ring with the most spread out parts up against the cylinder wall. We can also replace gravity in the pail experiment with linear acceleration, as per the elevator thought experiment. Edit: I guess the bit I'm not considering is if the local frame is rotating, and the pail appearing to rotate with respect to it, could the water be flat if the pail was non-rotating in the absolute frame? Seems really weird to picture it, but we could measure the radial acceleration of everything except the pail of water to see what's what.