the reverb isn't being applied to the synths in the M Machine song, it's being applied to white noise. Make a big spacey white noise reverb splash sound and group it to your synth, then sidechain the whole group. The synths aren't being drowned out with reverb, they just have a low pass filter that closes when the drums hit to bring the levels down and exaggerate the white noise sweep. You can hear the underlying reese type synth sweep back in as the filter is opened and the pluck follows a bit later.
food for thought - don't go crazy trying to emulate the M machine, or noisia or koan sound or even knife party to a large extent. Those guys are on a different planet when it comes to engineering. Definitely try and learn from them, but don't lose your mind if it doesn't sound perfect. They are the best of the absolute best when it comes to sound design and processing. Focus more on learning why certain things sound a certain way.
Things getting spacey doesn't always mean reverb, in fact it usually means the opposite. Space and ambience are created by leaving lots of headroom, reverb eats up headroom like no other. Closing a low pass filter and letting a subtle white noise patch sweep across and around the stereo field will do more for ambience than dropping a reverb bomb on a track or a patch. Create space, then use subtle, quiet and controlled elements to exaggerate that space.
