1) Seth cashes in to win it from Brock in a triple threat.
2) Vacant wins it
3) Roman wins it at Survivor Series 2015
4) Sheamus wins it
5) Reigns wins it back from Shameus
6) HHH wins it in the Royal Rumble match
7) Reigns gets his Mania coronation
8) Rollins wins it for two minutes
9) Dean wins it cashing in at MITB
When you break this down, all of it basically happened one reason or the other, because of desperately trying to get Roman Reigns over, or compensating for his failures to get over. Rollins holding the belt was so he could drop it to Reigns, which is why Ambrose didn't win it from Rollins when it made all the sense in the world. Sheamus won the belt because audiences loathed Roman winning it and they thought "We just need a heel to win it, so then he can win it against a heel!! Not just any heel, but the worst guy ever!!" When that didn't work, HHH had to win it to do the SAME thing they did with Sheamus/Roman all over again, which AGAIN didn't work
The main event scene for the last two years has been one long cycle of Roman Reigns FAILING.
The midcard/women belts matter less because those performers matter less to anyone in charge. There's probably people in the back who don't even know who the IC/US champs are. They gave up on the women's division the moment they realized creating Ronda Rousey wasn't going to be as simple as a Stephanie McMahon promo declaring this the "revolution".