Question

7. DFA's small-stock funds managed to outperform small-stock indexes and most other small cap funds. What are the main reasons for them to be able to do so?

Answer 1

I conclude 6 reasons for the out performance of DFA’s small stock funds:
1) Distinct Investment Strategies. Dimensional founders believed passionately in principle of "passive" stock market investing. As passive investors believe in the so-called efficient market theory, which maintains that almost no one can be smarter than the market as a whole in the long run. Hence DFA buy and hold broad portfolios of shares, betting that their returns over time will trump the gains of most "active" managers who try to find the stocks that would outperform the market.
Dimensional does not actively pick stocks or passively track

(2). Low Costs – low management fee to attract client
Their investment management fees are positioned well below those of traditional active managers. DFA's fees tended to be lower than those of most actively managed funds but higher than those of pure index funds. This was fitting given DFA's position in the market as a passive fund that still would add value. And this competitive and well-positioned pricing helped attracted client.