Originally, there were two forms that first were brought to the states from cuba. The first was pure Cha Cha Cha and was on 1, the second was Mambo-Cha that was a syncopated Mambo & broke on 2. The first form survived in Latin culture and the later was quickly adopted by US teachers. This is likely due to the prominence of music on 2 and ease of teaching one system of counting. It honestly depends on the song, which is on beat. Sam Cooke's "Everybody loves to Cha Cha Cha" breaks on 1 for example
Dancing on 1 is taught like salsa. Dancing on 2 is based on the mambo, which breaks on 2. Chacha is actually derived from mambo, so ideally breaking on 2 is correct.
In Chacha and Rumba, you dance the check (right foot backward for the lady, left foot forward for the man) on "2", i.e. "1" is in place, the 2 check bw, 3 check fw (lady), and "4 and 1" for "Chachacha". "On 1" does not exist for Chacha and Rumba, only for Salsa. These steps here look very nice, but it seems to be no ballroom dancing (at least no IDTA). Is it Street Chachacha ?
