Those links from pre-Christian water cults to the present , merely show the continuity and development of these religious and folk traditions.
Most were suppressed by the Puritans in Western Europe.
Well dressing is very limited geographically - but has similarities to the placing of garlands at, or in wells (which still happens) and may refer back to the annual procession of icons , statues etc to wells and springs on Saint's Day.
Also the effect of the cloth tokens at healing wells is similar.
Yes - one can only speculate how 'traditions' arise - but in the 14 century in Derbyshire they were not spontaneous.