My stepdad (66) was diagnosed with Type 2 about three years ago.
When they told him what was causing his symptoms, he nearly fell off his chair in surprise.
In his youth he was a sport-nut, as he got older he kept it up, walking, running, the lot - as a result he's as slim as a wand, and what my parents eat at home could not be any healthier; all home-cooked from scratch, no processed stuff, not many biscuits, cakes etc etc. They don't smoke, or drink much, either.
He's not found the transition to a diabetic diet too hard - after all, his diet was not unhealthy before. What he has done is to cut out sugary stuff like jam and fruit juice, and limited his carbs a bit more.
Don't beat yourself up, OP: sometimes these things just happen to us.
He does make me laugh when he describes going to the diabetes clinic though: it's full of huge people who literally sit there swigging from cans of coke and eating chocolate before going in to see the consultant....!