People also are quick to forget that our attendances were artificially inflated for a few seasons by new ground. Cup finals , premier league football etc.
This is probably our natural level.
The 30 odd years we spent in the bottom 2 division means that huge swathes of an entire generation of fans were lost to big clubs. One very forgettable season in the top league is not going to reverse that.
5-10 years up there and it would likely have a bigger impact on our natural level of support