My best theory as to why so many blowouts is that matches are done based on team power, and team power badly overstates the relative power of unleveled or partially leveled heroes when compared with maxed heroes of lower star levels.
My alliance has a high percentage of people who have paid to pull heroes and have a roster full of 4* and 5* heroes that are waiting patiently behind the ones we are currently leveling up. Some have a set of maxed 3*s; some got better heroes early and didn’t bother.
A free/cheap player, (who has a similar top-30 team power score, and has been playing longer) probably has one or two 5* heroes if any, will consist of mostly maxed 4* heroes, maxed 3* heroes, and perhaps get to unleveled 3* it 2* at the end, with only 5-10 partially leveled heroes.
There is no question that the latter team is way stronger. And my experience over the last dozen wars is that they seem numerically more common, as we keep finding them!