That is an elm. Yes...they were likely killed off by DED, but they put down a bunch of seed first. The juvenile trees don't get DED too often. At some point they lose that ability, get it and they die too after having produced some seed. Around here most die around 8-12" dbh. There are some 24"+ trees around...in fact I saw a big beautiful +/-30" dbh tree in the middle of the woods today.