I take it you are not in the US, because, separated by a common language, we have toilet "bowls" here, not toilet "pans". (And the etymology of that is actually probably at least a little interesting.) And we don't have "back to wall" toilets. We call them "wall hung" or "rear discharge".
What caused the break is unknowable. A crack or break there could be caused by a million things, given the material used and the manner of installation. Typically-permissible fittings in the US wouldn't look like that, perhaps accounting for our members' surprise, and statements above. And the result you have could be seen to validate the stricter US rules...
Would it be a big deal to duplicate that installation as a DIY person? Probably not much, at least as far as the "plumbing" part goes. The removal and reinstallation of the porcelain and perhaps a section of wall might be a bigger deal.