Well, tbh they're just 3 points ahead of us. And we're leveled on points with Sociedad B who were playing in Segunda last season. OTOH you have Bilbao Athletic who are second to last. In general whole league is very close together. Just 8 points difference between 5th Amorebieta who holds the last promotion playoff spot and 16th placed Logrones in relegation zone.
Another thing is these Basque teams are more depending on developing their youth teams than we are. Mainly Bilbao ofc but Sociedad have also promoted at least a player or two regularly over the past few seasons.
We also have the youngest team (average age just under 20 years). Bilbao Athletic are around a year older and Sociedad B and Osasuna Promesas teams both about 2 years older in average. Might not be as important if we'd be talking about teams with average ages around 25 years but when most players are still teenagers having younger/less experienced team it's clearly important. And based on a few games I've watched I think youth/inexperience were pretty obvious a factor in us not turning some draws into wins and losses into draws. At the end of the day we're still only 6 points away from the top of the table Eldense.