I don't see how it's a bs system. Are you expecting to just keep winning games in a row playing the same quality of players? It's perfectly logical the way it is. If you were meant to climb, we'd have an over-representation in Plat and above due to ease of climbing.
The statistic you've provided seem to be just coincidence. The fact that your W/L is that shows that you are going to climb. Promos aren't regular games, though. You fight higher level players due to the nature of proving your ELO. Wouldn't be fair to just play against equal level players there.
And yes, you could get "Trolls". Of course, troll in the League community means anyone not doing well, so the word has no merit. People are labeled trolls for bad pings, bad mechanics, bad decisions, overextending, etc. An actual troll is someone who builds 6 tears, runs down mid, follows a jungler stealing camps, etc.
You just happened to lose those games, and it's not Riot trying to fuck you. That's a self-serving bias used to excuse one's own performance or inability to climb. The odds are still heavily in your favor, ideally you should be at a 50/50 win rate. You're clearly far past that. But, being in diamond doesn't mean you'll just shoot up to it instantly as a smurf. Even challengers don't usually have a near perfect win lose because it's not a solo game, but a team game. You have 4 other human players per game, and each one has their own reason for performing poorly each time. It's not like a guy that does poorly is a genuinely bad player, we all have bad games. Someone could be in your game, lose with you, be dissatisfied with you, look at your lose streak, and determine that you're a boosted player. But, that's not the case. As with you can be with others.
Just keep playing. With your win rate, you'll be just fine. But don't be arrogant and expect 100% WR.