Background detail that may be helpful: USCP closes some House office building entrances at night/on the weekends/when Congress is not in session to ease workload on personnel. Those doors still function as exits for fire purposes (have alarm bars to open from inside). 
Bowman said he didn’t realize pulling the alarm would trigger an evacuation. He thought it would open the locked door he was trying to use to exit the building. “The door that’s usually open wasn’t,” he said. Bowman said he wasn’t trying to delay the vote. “That’s B.S.”
While Congress was in session, it was the weekend/unexpected and this entrance (looks like NJ Ave) is a main entrance normally, and the fastest above-ground route from Cannon offices to the Capitol. If Bowman was late for votes, it would make sense he would rush this way.
If this entrance is blocked, the next fasted route from Cannon to the Capitol is to take one flight of stairs down to the tunnel. Marginally less direct, maybe ~5min trip vs ~3min. Could make difference btwn missing a vote and not.
However, it makes ZERO sense that he’d think the fire alarm would open doors- they are emergency exits, just push them open! And if he pulled the fire alarm bc was worried about triggering an alarm by pushing the doors open, well- alarms don’t, like, cancel each other out.
But pulling the fire alarm in a House Office Building wouldn’t disrupt anything happening in Capitol/other buildings. If his intent (as some allege) was to delay votes, this was a dumb way to do it. Then again, the only other explanation is dumb too!
In sum, pulling the fire alarm was very dumb. Now Bowman will have to explain whether he did a dumb thing for dumb reasons (open door) or dumb thing for bad reasons (obstruct/delay). Fwiw, I’m here: “Never attribute to malice that which is adequately explained by stupidity.”