Sometimes it is hard to figure out why others do what they do. There were several dysfunctional/addicted folks in the family I married into. They did strange things in strange ways. Made sense to them in their way of thinking. Many times they and their actions made no sense to me. A councillor friend told me that it was like apples and oranges, their logic was not my logic, and it would always be that way.
Then add in the evil of meth, a friend's son tore apart their home under the influence of meth, it looked like a tornado had gone through the place. The next day he claimed he didn't remember a thing. A neighbour saw through a window and phoned the parent's cell. When they got home to the destruction, their son didn't even recognize them. Their son was a wonderful person until he tried meth, he was hooked from his first try. What a nightmare.
Maybe that is why much of what went on in the disappearance of Lyric and Lizzie doesn't make sense to many of us. Actions done by completely different mind processes. The riding around on the quad is an example. We see a time gap. Dan may simply see a father riding his quad looking for his daughter, searching again after the others had searched the same area.
Maybe he did what made sense to him, the way his mind was working at that time. Maybe driving around on his quad then made him feel like he was helping search for Lyric and Elizabeth, no matter what time it was? Maybe he had a feeling they were not in the lake, had been taken away, and he hoped to find and rescue them? Maybe he was riding around mainly to soothe his own conscience, or he was putting on a show? I don't know. It is very hard to fathom what is going on in someone else's mind, especially if there is dysfunction and addiction. imo