I've been playing this game for a while now, maybe once a day. Always my score is top 50%. I wonder how others get better scores and think, maybe next time. Today I played the daily level released at the first time possible. After finishing the game, the leader-board showed many other players had scored already and surprise surprise, higher.
It just seemed fake to me.

Just to shed a bit of light on leaderboard stuff, fake scores are actually extremely easy to submit on Steam, but the caveat is that hacked scores are much more rare on the Daily and Weekly Challenges, and the map-specific City Challenges. I occasionally do a sweep to remove very obviously fake scores (1,000,000,000, 1,234,567, stuff like that), and check for general trends in the leaderboards. Many of our players are getting 5k, 10k, even higher completely legitimately. We even had a legitimate screenshot with a score of over 100k on Reddit recently! Please feel free to sing out if you see something that is obviously fake, i.e. you are #2 on the leaderboard with 3k and the #1 score is 666,666, and I'll go in and clear it out. Clearing fake scores on Steam is a time-consuming, manual process, so we can occasionally get overwhelmed, but it's definitely something we try to stay on top of, and I do investigate and remove fake scores that are flagged by our players.

The devs stated that, in Mini Metro, for a certain period, they had to clean the leaderboard every day from fake entries. I'm not surprised that it could be also the case with Mini Motorways at the moment.

Some people just aren't able to play games with leaderboards in a normal way. Probably they want to show the world that they are 'the best'. For me they are indeed 'the best'. But not in playing the game. They are high up on the leaderbord of 'cheating and tricking',

Yeah I agree, I've been playing the game for while and think I am not bad at it. There are things you can do to cheat, but what would be the point?