Salam
(1) God does not know the future.
(2) If Angels didn't become prideful and to an extent near arrogant, humanity might not have been a thing.
(3) Iblis was an anomaly that left God between rock and hard place, kill him and make a lesson out of him...then every being would worship God out of fear in real time without God's reward and punishment being a delayed hidden thing. So instead he opted to make him the sworn enemy of all good people and the root of evil.
(4) Adam was expected to pass the test, is was unexpected an elite servant of God fail it, yet this didn't diminish the status of he being chosen, since he repented quickly and God knew and trusted him to be a lover of God and God's choice was not diminished.
(5) God could've made it that Adam is a light creature impressing even Iblis and that no trial happened in this regard, but the reward and ascending to God would be pale and heaven would be a pale place for most.
(6) Prophets and Messengers could've been so that there honor goes untouched, they can be not harmed, etc, but it would be too easy to believe, but as the potential to deny them is there, and trial more difficult, so is the reward.
(7) God is unseen but is manifest too, God his hidden and manifest, and the reward would be low if he was totally manifest like the way he will be on day of judgment. He has hidden the hour and greatest proof so that every soul is awarded for what it strives for.
If God manifested himself the way he can with full degree, then one of your top priorities would not be possible, that is a relationship with him in a meaningful way. Everyone would worship God but not on high terms and noble terms, but see God same way you see the physical sun, no big deal type thing, save a few of his elite servants would truly be close to him. Heaven would be meaningless for most, and we would almost suffer from boredom.
(8) The nature of the next world as outcome of seeds place in this world is the best type of afterlife. Now, God gambled with that, true, maybe if he knew most would go to hell, he would have chosen not to risk them for the few going to paradise. But that is 20/20 vision from the outcome after. God expected (but knew the possibilities and probabilities otherwise) that most follow Nuh and his predecessors and successors. But humanity has always rebelled since and the few believers who accept the chosen saviors would become ungrateful after being saved and delivered from their oppressors. Even the Ahlulbayt to prepare for Mohammad (S) and his family (a) were questioned, opposed, starting with Moses (a) being questioned and giving a hard time as well from his people.
(9) The miracles of Prophets are a soft spot between God being hidden and manifest, but it's more on the day light manifest side, while when there are no signs in the open, it's more of on the night side. The reason for delay of such signs and miracles is because the previous generations denied them and made it impossible for God to guide through them without the followers of the guides performing them being in oppressed state. God to delay punishing generations of people and not destroying the world and saving cities from being destroyed has delayed that result which is a big warning in Quran, has hidden the last guide for now. However, you can pray to God for guidance and hope God will allow you to be guided by the guide and meet him and be shown miracles through him.
(10) We are more on the hidden side of God's hiddenness than ever, because of the long delay of Imam Mahdi (a). However, the Quran balances this a bit since it's full of miracles but the type that you have to reflect to see and do a bit of more effort. The Quran is a sufficient sign and proof, however, it would be nice to have the guide back in the open.
TL : DR - God chose to be hidden more so to offer a rewarding experience in the next world with him, then opt to manifest himself for a pale end world and low reward. He has chosen to honor believers and punish disbelievers, however, perhaps, if he knew before hand how little believers there be and how many disbelievers, the trial would have not been opted. Even perhaps humanity not created in the first place. However, God is doing his best to fix the problems with constraints. And one of these is that he won't break his promise to respite Iblis and continue to allow him to challenge humanity and try to degrade them.
