Was the attempted assassin of President Trump, 20-year-old Thomas Matthew Crooks, manipulated by the Extraterrestrial Alliance to carry out the shooting?

This is definitely the case. They cannot resist upping the ante, taking extreme and even reckless chances with their own plans and orchestrations simply to increase the tension, raise the stakes, and add excitement to the unfolding drama. Keep in mind, they take no risk personally, except for those imposters in the field who are indeed in harm's way being on display and are physically vulnerable to things that might happen spontaneously, including accidents and illness. While they have wanted Pres. Trump to be in charge in the past, they have seen the harm Pres. Biden can do and his administration and it is more to their liking. So they are willing to switch horses in midstream, so to speak, because it makes for an interesting plot twist.