The thing about these accumulators that you need to see is that they are messing with your mind. They tend to give the feeling of 'allmost winning' which is processed in the brain very similar to actually winning. They are addictive since most of the time they feel like you made a great call but got unlucky. It gets most people who bet these in a mental state of denial. When just running the numbers on combo bets they simply don't hold up.

It's what is difficult about sports betting, the sample size to give numbers meaning needs to be huge in order to eliminate randomness. If you ever get to a big enough sample size things might have changes so you are never sure. If your predictor manages to predict these kind of things systematically you could be a millionaire in no time. Most of the time this is not how things go down in sports betting as edges tend to be small.

Good luck !