They are just cheap chocolate with cheap licensed figures.

Kinder Surprise eggs are illegal in the US, as federal regulations deem them a choking hazard.

https://en.wikipedia.org/wiki/Kinder_Surprise

A 1938 law, the Federal Food, Drug, and Cosmetic Act, prohibits confectionery products that contain a “non-nutritive object”, unless the non-nutritive object has functional value.[34] Essentially, the Act bans “the sale of any candy that has embedded in it a toy or trinket”.[35]

If Pope Francis actually gave Vance’s children Kinder Surprise eggs — as opposed to some other type of chocolate egg — we can reasonably assume that the pope was trying to murder Vance’s kids, and that Vance probably felt that he had to strike before the pope made any subsequent attempts.