When the server drops a large number of players (sometimes everybody) it's likely one of two things:
1) A server crash
2) A connection drop
Here's how you tell the difference.
How to tell if it's a server crash:
-The rounds won on the scoreboard will be zero for both teams, or very low
-The map might be different (i.e. you were playing on mlcastle but now after reconnecting the server is on space)
-The map time remaining might be inconsistent with what it was before the crash (i.e. there was 30 minutes left on Snowday but after the crash now there's 1h 10 minutes left)
How to tell if it's a connection drop:
-Not everybody disconnected! You can tell this by "Viewing Server Info", sorting on the Time column and then seeing that someone has high playtime
-Each team has more than 0 or a few wins in the scoreboard
-You come back and the map is the same with roughly the same map time left
Some things to note: the map and timeleft will probably be identical during the Minecraft offhours, regardless of crash or connection drop
Because of this, the best way to tell which it was is based off of the rounds won for each team
