太 is simply 大 (big) with one extra dot — 'bigger than big', the greatest, the utmost. From 'supreme' came the everyday intensifier 'too / extremely'.
太 means 'too / extremely', and it loves the pattern 太…了: 太好了! (Great! 'too good', reusing 好 and 了), 太大了 (too big), 太贵了 (too expensive), 太多了 (too much, with 多). It can be positive (太好了 = wonderful!) or a complaint (太慢了 = too slow). 太 also means 'supreme/grand' in titles: 太太 (tàitai) = Mrs./wife, 太阳 (the sun, 'supreme yang'). One small dot turns 'big' into 'too much'.
大 (big) with an extra dot — bigger than big: TOO, extremely.
太…了 is the go-to exclamation: 太好了! (great!), 太贵了! (too expensive!). And 太 means 'supreme': 太阳 is the sun ('great yang'), 太太 is 'Mrs.'.