There are military men on both sides, but a huge majority is on Bolsonaro's side, especially the military types who actually hold the keys to the armories and bases.
And Lula's clique has attacked the Army indeed. They are saying they will appoint a civilian to lead the Ministry of Defense, a first since... Well pretty much ever I think. They have also soured relations with the Police forces, both the Military Police (saying they want to disband it, returning it to being only a police for Army and Military bases and matters) and the Federal Highway Police (The people in charge of keeping the highways and most of the borders safe, down to both floating a literal commie who wants to decriminalize drugs and who thinks we need to take race and social status when deciding to arrest people abd wanting to fire and prosecute a big PRF officer for campaigning for Bolsonaro)
Things will get a lot worse before they get any better. We have out own Qanon type "2 weeks guys" (the meme here being 72 hours to The Big Thing) but said thing isn't really anything more than a strawman. The actual dissatisfaction is coming from truckers and farmers refusing to play ball.