Recently I was GMing a D&D 5e party with my friends online, and for the most part we were having a good time, but in a recent session we hit a rather large speed bump. I had an easy encounter setup for them so that they could roll through the story arc fairly quickly. To my surprise the group spent almost an hour of play time to try and think of ways to trick this enemy group with illusions. One person in particular seemed to think that they had to think their way out of the box instead of handling the encounter in front of them. Let's call him Tom (not his real name). Tom is a fighter and likes to be a strategist of a sort. He wants to out-maneuver the enemies 9 times out of 10 instead of actually fighting things.
It's a valid play style. But this encounter was set up with an easy difficulty because we've had a lot of deadly difficulty encounters before that and have since wanted quicker combat. The enemies in question were some fishmen and their high priest who had captured the captain of the ship they purchased passage on in order to reach a new town. I had thought the fear of the captain being harmed would propel them to take quick action which is why the combat was set to an easier difficulty. I wanted them to feel like combat would be quick since they had just gained levels and were using some new spells.
Tom wanted the bard to cast a spell Tom knew about because it had been used before (Phantasmal Force) in order to trick their high priest into making a pseudo-god. The bard (Let's call him Frank) refused because Frank was skeptical of the plan. So then a very long winded discussion between the Fighter(Tom), the Monk, and the Bard took place. Eventually Tom and the Monk started their own conversation about the plan leaving the rest of the party just standing around.
(They could have this lengthy conversation because combat hadn't started yet and the enemy wasn't aware of them: the party at the time were being stealthed by the Shadow Monk's ability. They had used Shadow Arts to cast Pass Without a Trace.)
Eventually Frank decided to take matters into his own hands and casted Hypnotic Pattern on the enemy group. This caused infighting among the players because the Fighter and the Monk wanted to come up with a super-clever plan that was way over the top and unnecessary to the encounter. The Bard was tired of being ignored by the two players who were the only ones having fun devising a stratagem. The Cleric and Druid were basically checking their phones in the meantime while they had nothing to do during this whole hour.
So to my question:
What could I have done differently to make this encounter more enjoyable for everyone instead of an hour of discussion / infighting?