If I remember my history lessons correctly -

Part of the reason that the 27th was chosen was because for the months immediately before the event, it had been on obscure training exercises and generally out of contact with the general public.

Other military groups that had access to the news and had been in contact with the general public had already shown understanding with the protesters (or were at least suspected of being sympathetic), so it made sense to use a group which had completely missed out on recent politics.

The leadership was then able to “sell” to it their version of events (that the protesters were rioter, unpatriotic and working on behalf of foreign agents) to tee them up before sending them in.