I'm wondering why I showed up on a Friday at 3:45 to check out the park and go fishing and I can get in the parking lot but the gates are all locked to get in the park?

Interesting indeed.

Some days, I believe weekends, you park in the parking lot and a tram comes along and takes you to the park and some day, I don't know which, it's just closed

If you came on a Friday the front main gate to the park will be open. The gates at the off-site parking lot will be closed, as it is not used Thursdays or Fridays.