Whether it was originally flat topped involves some interesting speculations....

If it was needle shaped then the builders are owed less admiration - anyone can build a big tall thing that's visible from everywhere, but if it was deliberately at that height, so it peeps and hides in the way it does, that's impressive.

IF the height was deliberate, and an exact sight line was meant, there's 2 possibilities - either they were seriously miraculous surveyors to plan it that way, or they just banged it up and stopped when they could see the exact height they wanted, hence the truncated top.