arrive at, reach, intelligent, smooth, slippery
达 centers on reaching a destination or state: arriving, attaining, or becoming smooth and unobstructed. The meanings 'intelligent' and 'slippery' extend from the idea of things moving easily and without hindrance.
达 is a simplified form of 達. The older form combines 辶 (movement) with 羍, which likely contributed the sound and the idea of smooth passage. The modern simplified inner component 大 is a visual reduction and does not carry the original phonetic or semantic role.
The movement radical 辶 surrounds 大 (big). Imagine a big person striding smoothly along a path, arriving effortlessly at the destination.
For タツ, picture a big person arriving at a tats (tats -> タツ) convention, moving smoothly through the crowd.