I can see what you mean, and I agree with you that in this particular case, the sentence is not quite correct. Remember that Wikipedia is written by the public, so the grammar is not always perfect. The author of this sentence was aiming for a structure like this:
"Twenty stories high, this building towers over the other buildings in the area."
"Made with fresh fruit, these drinks are healthy as well as delicious."
In these sentences, it's clear that there's just one subject, and the first part of the sentence is a description of that subject. So one subject has two descriptions. We could instead say "These drinks are made with fresh fruit AND they are healthy as well as delicious." We can also reword these sentences so that they look more like your example:
"A twenty-story edifice, the new building towers over others in the area."
"A blend of fresh fruits, this drink is healthy as well as delicious."
The subject of the sentences hasn't changed ("building," "drink"), but there are now nouns in the opening descriptions, too ("edifice," "blend"). Again, we could reword the sentence to make the connection clearer: "This drink is a blend of fresh fruits AND it is both healthy and delicious."
This kind of sentence structure does sort of imply a causal relationship or an explanation (the drink is healthy and delicious BECAUSE it is a blend of fresh fruit), so it would be perfectly appropriate to use "as" at the beginning. But because the causal/explanatory relationship is implied by the structure itself, it's not necessary to say "as."
The sentence you quoted does seem wrong to me, though, because instead of "made of fresh fruit, this drink is healthy," it says something more like "made of fresh fruit, this drink's vitamin content is high." The vitamin content is not made of fresh fruit. The country's size is not a megadiverse country. So I agree with you that there are two subjects here, although most readers will assume that "country" is the subject.