This is an incorrect assumption.
Q does not need evidence for courts as the courts will never prosecute. That is impossible. At best, the military can prosecute under tribunal - in which case the process for determining guilt does not revolve around how information is collected or submitted.
Think more simply. Would people believe if Trump stood up and said: "the military will be prosecuting criminals for crimes using evidence we have collected secretly?"
Of course not. The people must come to question reality and their role in the world. The public must believe there are crimes to be investigated - that there is something wrong with the established system.
Q did not need our help to uncover evidence. Q simply needed the question to be injected into the system. Over 90% of all content on the internet has its origins in boards like halfchan - which is precisely why Q showed up there in the first place.
Q knew that it would take only days, if not hours, for the posts to go from 4chan to the conversations of politically active forums everywhere and from there would embed itself into the conversation, permanently.
Q successfully gave the impression that she was frequently in the company of President Trump, though President Trump was no doubt aware of Q before we were.
Remember that Q is not here to be our pen pal. Q is here to achieve the ends of special warfare.
All of this was well defined in advance.