Yeah, the only crazier thing would be to replace CNG (~39GJ/tonne) with something even more energetic like Diesel (~45 GJ/tonne) or Petroleum (~47 GJ/tonne).
Diesel is surprisingly inert; I've sprayed it across hot engines when bleeding injectors but I wouldn't do that with petrol (and probably not LNG).
Inert and "has a relatively high flash point" are not the same thing. I was around then someone foolishly incinerated a can (metal 5L type) that had a very small amount of red diesel left in the bottom (~50ml). The ensuing explosion was non-trivial, but fortunately did no harm.
The individual responsible, Nick, also once tried to 'pep up' a damp and lack-lustre camp fire by tipping petrol on it. Obviously there's something to owning a Norton Commando that rots your brains because both the Commando owners I've known [Nick and one other] were prone to bright ideas of this ilk.
This explosion you refer would have been the same with or without the red diesel which is only small amount of dye added to enable law officers to distinguish between diesel used for road use and therefore has had the proper added taxation paid, and diesel used for a purely off-road use such as farming, and this diesel has the red dye added.
https://www.utilitysmarts.com/automobile/diesel/whats-the-difference-between-red-diesel-and-regular-diesel/
A 5 litre can with a small amount of
water would probably explode, too, but it might take a tad longer.
During WW2, my Dad worked at a foundry where salvaged bits of steel stuff were placed in a furnace & melted down for the War effort.
One day, a massive casting which had obviously been sitting round in the weather for years, turned up.
Partway along it was a small hole, sealed with a steel screw in bung.
In it went, the furnace as fired up, it got up to temp, & suddenly, there was a deafening bang, & something flew through the top of the furnace, knocking a decent sized hole in it.
Dad, & all the other veterans of the Kaiser's War, hit the deck!
Of course, the Military were all over it, but it turned out to not be Japanese Commandos, or a "5th column", but simply that there had been a small amount of water, somewhow captive under the screwed bung.
The resulting superheated steam blew the bung out of the moulding & through the top of the furnace.
Of course, that would be quite a few orders of magnitude more powerful than a bit of something in a can!