Essentially it was question casting of this size being automated at car maker scale. Bigger castings were integrated before on assembly lines, but at higher costs and complexity before Italians made the large mostly automated caster that Tesla called GigaPress (iirc) - it's essentially COTS factory equipment.

What's actually new and interesting here is the combination of size and speed. Sure casting existed, but for it to be the backbone of a super fast production line like that of a Model Y, they needed to do a lot of work.

Larger parts were often dipped into liquid, because air cooling resulted the part bending.

Tesla internal materials team worked on new alloys to improve this, while working in coordination with the machine manufacture to get up the cycle times.

And they are continuing to work with them. Tesla is using newer more advanced cooling systems in Texas then they did in the California factory. Because cooling is one of the limiting factors in Cycling these machines.