I feel like he took a page out of Cleetus's book doing crazy silly stuff for the views and then it just took off. His one video of 11M views was his attempt at using a truck as a boat locally. Basically it floated and was towed by a another boat if not being pushed by the crazy current at the location his dropped in at in my area.
I can't speak for his rise to fame, but at his current level, a lot of automotive YTers try their hardest to not mention money, and don't talk about any "hate" they get. They try to keep their channel very 14 year old kid friendly. WhistlingDiesel has gone the other route, flaunting the money, calling out all his haters, and that has amplified his views by a LOT. Last week or so he had the number 1 trending video on all of YT.