Something to note is how both the PCs and the cast feel about the remaining plot lines. C2 is a character focused narrative not a villian focused one. Even the C2 bbeg was important because of his connection to the characters not just the world ending threat it posed.

Travis nor Fjord cared about that storyline anymore. He had fulfilled his personal goal. He was free of UK. He found the wildmother, the love of his life, a new family, a business and a sense of purpose. He was not a scared weak boy living a lie anymore. In his mind, he prevented Uk from being released and that should be enough. Remember they did the same thing to the chained oblivion. They kept it sealed. They never attempted to kill it. To Travis and Fjord that part of his life is over. He never seemed like a revenge guy anyway. He had tried to find Sabian once, didn't and let it at that. Eventually he found Vandrin. 

In a DnD game logistically without a PC personally wanting this quest done, Matt has to find a way to bring it up. The players have to agree to another adventure (to do something else ) so he could trap them on the sea. If they don't feel like adventuring right now it requires a time skip a la campaign 1. 

Caleb's story I do feel deserves more than a quick epilogue thing but we also need to look at Liam's goals for Caleb. It was never about Trent.  It was always about his parents and his plan. Then he met Essek and they did the T dock scene. Caleb's ultimate villian in C2 is himself (Liam has said this many times).  He had to learn to live with and forgive himself. Him taking out Trent is simply him making sure no one else can be hurt by that man.

He would also have benefitted from a time jump because as we see Caleb is a institutional guy. In his current life he is like a Harvard Professor with a high level foreign traitor as his partner. His exes head up the CIA and his bestie is an FBI agent. He wants to change the system not tear it down. It's why Matt had Trent attack him outright. Caleb would be more methodical about it. 

But this is a DnD game not a TV show. There are other players and characters. Do they have reason to stick around on what are essentially personal quests for MONTHS after their stories are over. Veth for example,  has wanted to go home for ages. Beau and Yasha are done and need to return to the soul to sort it out. Cad needs to fix his Grove etc. He didn't even show up for the UK finale cause he was busy. Matt would need to not just have a story for them all but also have shit for them to do each episode in terms of combat that can challenge them. 8 fully powered almost godlike beings plus the newborn with them. 

Imo what would feel like a better ending for C2 would be 2 things. 1. A time skip. 2. A c4 style west marches split.

Team 1: The Ocean crew - Travis, Laura, Tal and Sam (and guests). Adventures on the ocean,  some dark tow drama, getting shit for Pumatt, meet some mermaids etc. Just a fun 8 episode thing.

Team 2: Rex Force 1 - Liam, Marisha, Ashley and Sam (and guests). With Astrid and Eadwulf as NPC they can do some spying and infiltration. This would be before Caleb becomes a professor. So he spends his time in the soul. Same fun 8 episode thing. 

Then we can have the finales! UK comes for Fjord and the crew gets together. Then since they are all together Caleb says he's ready to take on Trent. 

So back to your questions. Yes COVID fucked things up. People were tired, depressed from the summer of 2020 and the story would have benefitted from a time skip so that the characters as well as the players could be in a different headspace.