Extraordinary fantasy with bizzare and dark storyline (Spoilers)

Rating: 4/10 (19 May 2018)

Caveats on this review are; I'm no especial fan of comic book storylines made into films, my primary reason for attending was to take my children for their entertainment (not mine).
As you might expect from a comic book rendering; the central plot of revolves around Thanos (the 'baddie') intent on decimating humanity by ~50% of it's current number to 'restore balance' to an over-crowded universe that has dwinding supplies and no means to support the ever growing populus. Taking that and the film at face value - this is a bizzare and macarbe storyline that hurtles between fight scenes without any character development or sub-plot development whatsoever (O.K, that's a little unfair - but not much). That's maybe my own fault - as I've not seen the other (precedent) movies in this series. However, as entertainment value goes, it's a little poor and in retrospect I would not have taken my children to see it.
Now, taking the central plot as something 'other' than just fantasy I have a couple of questions / statements:
1. Is the storyline in anyway faithful to what was written in the comic book storylines?
2. Who signed off on the budget of this movie? - I'm guessing it cost $$$$$$$ (that's seven, each representing a 10-fold increase in magnitude) at least.
3. Whoever (individual or committee) did sign off on this budget, then also implicitly (or maybe explicitly) approved the premise of the central plot.
4. Given that Hollywood has been used historically to influence audiences and therefore by extrapolation (largely developed world) populations via it's 'messages' (propaganda) is this warning or threat?
5. I don't believe that a movie of such an incredible budget is signed off without having an ulterior motive (usually paving the way for later films and more money) - and unless I've missed something - they just trashed the franchise??
Just because I'm paranoid, doesn't mean they're not out to get me.