I can’t say there is no mental illness involved because in some fashion a lot of individuals who convert to islam have some sort of issue. For example, the female convert usually has low self esteem and the male convert is usually angry and feels isolated from society. Or the male convert seeing how their religion is being denigrated day and day out is looking for an acceptable religion in which to belong. This is the typical convert in the west. When Islam penetrates the penal system and recruits (mainly blacks) in prisons they do so preying on their lack of self esteem and longingness to belong to a group. Islam comes along and tells them what they want to hear. It may not make logical sense to you or to me but the fact that their so-called prophet started recruiting the criminal element from the very beginning means that they have a huge head start on us. Mental illness, maybe. Their proselytizing techniques prey on the vulnerable to add numbers to their ranks. Muslims when you speak with them always tell you how many of them there are in the world, albeit it is usually inflated by a lot. They will quote stats from polls to favor them. Its not a mental illness its a sales technique that preys on the vulnerable to recruit people into their ranks.
For example muslims used to say there was 1.2 billion muslims but when analyzed that number was below 1 billion. Today their quoted number has risen to almost 2 billion. This is what I mean by inflated number.