Breakdown of Na sajmu vlada kaos jer svatko traži šaren balon.
jer
because
tražiti
to look for / to demand, request
na
on, at / to, onto (with motion) / about (thinking about)
svatko
everyone, everybody
Questions & Answers about Na sajmu vlada kaos jer svatko traži šaren balon.
Why is the universal pronoun svatko used here instead of another case, and why does it take a singular verb?
Svatko means "everyone" and is in the nominative case because it acts as the subject of the second clause. Even though it refers to a group of people, it is grammatically treated as a singular "he/she/it". That is why it pairs with the third-person singular verb traži (is looking for), not the plural traže.
šaren balon is the direct object. Why doesn't it change its form for the accusative case?
It is actually in the accusative case! Because balon is a masculine inanimate noun (a non-living thing), its accusative form is exactly the same as its nominative form. The adjective šaren (colorful) matches this. If everyone were looking for a living masculine noun, like a colorful dog, the animate ending would be used: šarenog psa.
The translation says "chaos reigns". Is vladati often used for abstract concepts like this?
Yes, very often. Vladati literally means "to rule" or "to reign" (like a monarch), but Croatians frequently use it to describe prevailing atmospheres or situations. You will commonly hear phrases like vlada panika (panic prevails) or vlada tišina (silence reigns).
What happened to the second "a" in the word for fair (sajam) when it became na sajmu?