Having your followers storm the parliamentary buildings is indeed a classic step in a coup, but in order to make it stick you also need your followers to occupy the parliament, run off (or kill) your opponents in parliament and have the rump vote to give you the powers you want. And all this is really step two, where step one is to grab enough control over armed state functions so that police and military do not interfere with the occupation and afterwards prevents other groups from interfereing with the occupation. And while police seems to have stand back and let Trump followers get into the building in the first place, it seems to have been the common non-interference applied to far right protestors in the US rather then coordinated policy to let them occupy the building.

A poorly planned and ham-fisted coup attempt, but a coup attempt all the same. Not that I expect anything to come of it. It is one thing to impeach presidents over process crimes or failure to keeping up a proxy war (in the words of former National Security Council official Tim Morrison: "The United States aids Ukraine and her people so they can fight Russia over there and we don't have to fight Russia here"), but holding former presidents responsible for their crimes would go against "when the president does it, it means it is legal" as Nixon put it. And then where would the US be with all the things the state does that goes against the laws as written?