1. No, it's just something that has happened.

2. Any level of active management would make an index fund not an index fund. You'd be going to trying to pick the best-performing stocks, which is not what an index fund tries to do (capture the overall movements of the market).

3. The general advice is to have approximately a 65/25/10 split between SP500/international/extended market funds. You can adjust as desired.

4. Stock index funds are great for long-term investments, not so much for shorter ones. You can look at bond funds as well. If you have a good amount already (>100k maybe) you can schedule a free discussion with an advisor at places like Fidelity/Vanguard/CS and have them run you through the basics.