One cause mentioned in research is through a denial-of-service attack on the router using a known DDoS tool.
[1] Because packets are routinely dropped from a lossy network, the packet drop attack is very hard to detect and prevent.
If the malicious router attempts to drop all packets that come in, the attack can actually be discovered fairly quickly through common networking tools such as traceroute.
However, if the malicious router begins dropping packets on a specific time period or over every n packets, it is often harder to detect because some traffic still flows across the network.
Because wireless networks have a much different architecture than that of a typical wired network, a host can broadcast that it has the shortest path towards a destination.