Adware calamity. Tablet not usable. Help!

Dear people,

I was recently shocked to discover that I'm one of the unfortunate ones to own a tablet that came from the factory with pre-installed adware.

The adware in question are 2048, Tap Black Tile, and File Explorerr (with two 'r'). The latter was definitely present upon purchase, the other two not, but are simply impossible to get rid of.

I have a few questions:

1. I tried the common advice of rebooting in Safe Mode, then removing the adware. Doesn't help, it comes back. The adware doesn't have an entry under "App permissions". Why should the adware come back if I removed it in Safe Mode?

2. How can it be that numerous malware-removal apps that I've tried don't detect my adware? I thought the sole purpose in life of MalwareBytes and co. was to remove the infamous 2048 adware and its friends. My tablet is severely infected, with adds popping up every 30 seconds, yet this isn't detected. Any explanation?

3. Some of the adds that are displayed are from legit providers. For example, I'm getting lots of adds from Deutsche Bahn (the german train company), from real banks, from real apps and games on Google Play. I'm very curious about the chain of food here. What's actually going on? Deutche Bahn representatives meet in dark rooms virus composers and pay them money under the table in unmarked bills so that the latter create viruses that show DB adds on tablets? Doesn't make any sense.

4. I'm trying to understand the commercial incentive of the adware people. If somebody's tablet becomes unusable due to constant adds of Calvin Klein's new fragrance, this person wouldn't normally run to the shop to buy the perfume. They would try to remove the adware, swear to never buy anything by Calvin Klein, and tell all their friends on Facebook. So do adware writers actually earn money? This is beyond me. Please explain.

5. I've read that millions of tablets and phones come pre-infected. Yet it seems that most people are able to use theirs just fine, perhaps with an occasional add now and then. But my tablet is now bricked. An add pops up every 30 seconds and freezes the tablet completely. This isn't fair. Why does the situation on my tablet seem to be so much worse that normally?

6. Any advice on how to make my tablet usable again? I've read something about "reflashing" my Android. But I'm a layperson, this may be above my league (?) And besides, my tablet is a Chinese no-name, so I suspect I can't just download a clean version of my OS just like that. Or am I wrong?

Please help! Thank you...