In Ceuta women and unaccompanied children were being predated on by the locals (Spanish) and other migrants. In the very long journey most migrants take they will be extremely vulnerable to rape by the people smugglers, other migrants, random locals (there was a big issue with very young boy refugees in Italy being offered food for sex by local Italian men at one point), migrants recruited by the local police to push back other migrants (the Greeks did this. It does seem to filter for the worst people at the expense of the most vulnerable), and border guards themselves.
Don't forget that when the UK home office rolled out it's homes for Ukrainians scheme there was an influx of lovely British men wanting to offer homes to only young women. And early on reports of German brothels trying to recruit them (this is illegal sex trafficking). Because the routes for Ukrainian women/children were legal and regulated the UK government was able to crack down on this and change the rules on the homes scheme. It was easier for Ukrainian women and children to leave because of this which is why more Ukrainian refugees in the UK are women than other groups of refugees.
The current situation with boat crossings etc is horrendous and puts innocent people at risk while enriching smugglers and illegal gangs. But smugly trying to turn it into a political point along the lines of "see we told you male migrants are all bad people" assumes that all the rapes were committed by migrants. And I bet they weren't. It does provide a good reason for why the people taking this route are more likely to be male (though young boys are also preyed upon enroute. See my earlier point about Italy).