Was the RBMK-reactor revolutionary?

Hi guys,

Im recently becoming intrigued by the history and working procces of chernobyl. And this question may have been asked a couple of times but using the search button I couldnt really find it.

Was the RBMK reactor that the USSR used revolutionary? I mean yes we all know it had the negative pressure coefficient issue and the tips of the rods made the reaction unstable.

But a PRO was that you could switch out materials without turning off the whole reactor.(online refueling).

So in short: was there a reason the USSR had chosen the RBMK design over "water" designs (not political motivated)?

My apologies if this is a stupid question.