I don't know where you're getting the "formal procedure" for annexation not being followed. Congress changed the law on this to initiate annexation, and McKinley signed that and subsequently moved forward with annexation without the need for a ratified treaty.

The state then subsequently went through the actual statehood process many times.

There was obviously major opposition throughout the process, especially by a native majority who pushed the senate hard to disapprove the original treaty, lbut this was ultimately defeated via the change in law for annexation.

The president absolutely signed the joint resolution by congress to change annexation rules and then subsequently did so.

Cleveland supported the Kingdom of Hawaii, but McKinley subsequently trounced it and basically gave Dole the governorship.

You can't just say "the US government supported the Kingdom of Hawaii". The US government is made up of thousands of people, holding variable positions on things. The US governments interests change with the leadership.