The principal authors of Obamacare wanted single payer, but didn't have the votes. Short of single payer, they wanted a federal option or a national exchange, but didn't have the votes. So they settled on state exchanges, with the states incentivized to participate "voluntarily." This is a common means of dragooning the states into federal programs, but it didn't work this time.
What the majority of the Court has now done is give the advocates of Obamacare the national exchange that they clearly lacked the votes to enact at the time.
“Roberts took the view that Congress intended that people have access to subsidies”
Isn’t that a tricky statement since Congress operates to express its intent through legislation. Could you possibly mean that the architects of Obamacare rather than Congress intended that people have access to subsidies?