For those who don't know, the senior author on this paper (Sepp Hochreiter) was the first author on the original paper with Schmidhuber introducing LSTMs in 1997.
At least in biology, the first author of a paper is more often than not just a pair of gifted hands who did the experiments and plotted the graphs. Doesn’t always translate that they become good PIs later (though they get their chances from these papers).
In ML, it generally is ordered from most contributor to least contributor, w/ heads of the lab last.
In this specific case, it's fairly well known that Hochreiter was the major brain behind the original LSTM.