Don’t you judge me.
T is one of the more stable symbols. If you look at the alphabet gif, you’ll see it’s always pretty much two intersecting lines. It’s funny because some versions of T are, well, on a slant. Latin’s parent alphabet, Etruscan, has similar weirdness with T, with some versions tilty and some with only one arm. I guess when there’s no computerized fonts (or even a printing press), it all depends on whoever’s writing it.
T is much more stable in Greek, where it’s always a T or in lowercase, τ. I guess when something’s not broke, you don’t fix it : ). The Phoenician consonant alphabet that gave birth to the Greek had a bit more variations, using a simple cross that looked like a + sign as well as another tilty T. Whatever it looked like, the symbol was called teth and it meant “mark”, as it was in the proto Sinaitic it was taken from.
Well, that was an easy one.
TL;DR: T’s pretty much always been T :P.