The dive team that found the car addressed the issue of the original searches not finding anything. According to them, the sonar technology that was used in 2013 would not be as advanced as that used by the current team and the original sonar equipment may have been even older than 2013 technology. According to the current dive team, it would have been very easy to not be able to locate the car in 2013. The current dive team, as I recall, couldn't find it on an initial search, however they changed the sonar settings and tried again. That is when they finally spotted it.
The current dive team was pretty emphatic that the previous failed attempts to find the car was not unusual and was not the fault of the searchers. This info comes from the youtube video posted by the OP.