Professional mathematician here. That can occasionally happen with much less important papers; e.g. someone is asked to referee something, and doesn't really f

Professional mathematician here. That can occasionally happen with much less important papers; e.g. someone is asked to referee something, and doesn't really feel like actually reading it but would still like to see it published. If they are not conscientious they might only briefly skim the proof and write a hasty referee report. But ABC is a major claim. The community will not be nearly so quick to reach a consensus. In particular, from what I can tell now there are a handful of mathematicians other than Mochizuki vouching for the proof, but even that is still not enough: overall, the community has yet to come to a consensus that this is enough.