在 combines 土 (earth) with 才 (a sprout breaking ground). A sprout rooted in the earth is PRESENT — it exists, right here, in this place. From that image comes 'to be at / to exist'.
在 is essential glue. As a verb it locates you: 我在中国 = 'I am in China' — the very sentence 中's lesson set up. As a marker before another verb it means 'in the middle of doing': 我在吃 = 'I am eating.' One small character handles both 'where you are' and 'what you're doing right now'.
A sprout (才) rooted in the earth (土) — PRESENT, existing right here.
在 doubles as the 'right now' marker: put it before a verb and you're mid-action. 我在看 = 'I'm watching.' 我在听 = 'I'm listening.' Your new verbs come alive in the present tense.