Learn Dutch: Vanwege de drukte is de weg dicht. - Due to the crowd, the road is closed.

Because the sentence starts with the phrase Vanwege de drukte (Due to the crowd). In Dutch main clauses, the verb must take the second position (the V2 rule). Since the reason takes up the first spot, the verb is must come next, pushing the subject de weg into the third spot.

Could I use wegens instead of vanwege in this sentence?

Yes, Wegens de drukte is de weg dicht is completely correct. Both prepositions mean "due to" or "because of". Wegens sounds slightly more formal and is heavily used in official traffic announcements, while vanwege is extremely common in everyday conversation.

The word drukte is translated as "crowd" here. Is it related to the word druk?

Yes! It is the noun form of the adjective druk (busy). While it translates to "the crowd" in this specific context, de drukte more broadly means "the busyness", "the congestion", or "the hustle and bustle".

Can I say the road is gesloten instead of dicht?

Definitely. Gesloten (closed) and dicht (shut/closed) are synonyms in this context. Dicht is shorter and very common in spoken Dutch, while gesloten sounds a bit more formal, like something you would read on an official road sign.