So, they took the standard shipping container for granted.

Yes, at the time the container was breaking through. At first the standard 20ft and 40ft containers where mostly a US Army innovation (well, that’s what they claim, it was a Dutch lad that actually came up with the idea. The US Army just gave enough critical mass to make it popular). Since the US Army wanted to use these containers, and the 747 was originally intended for USAF use making the 747 compatibel with the container was just logical.

Can DC-10 and Tristar accommodate those standard containers?

No, I do not think they can. Even if they could, the cargo hatch is no way big enough. Perhaps a 20ft but you would have to wiggle it around whole lot before it gets in!

Which planes had those “standard aircraft cargo containers” been invented for?

Pretty much all of the jets! However, until the advent of the A300 the container would be used on one side of the hold, and the other side of the hold got another (smaller) container or loose cargo.