"Bitcoin is a mystery to me. Somehow it's hailed as revolutionising the economy, by replacing currency with a worse kind of currency."

The coin/currency thing is misleading. You should compare it more to gold than to USD etc. Something off which the issuers can't conjure up 4 trillion out of thin air whenever their palls want 'moar!'. USD would be completely Zim dollas by now if it weren't for the petrodollar scam.