I would define a "box office bomb" as a movie that can't even make back its production costs (marketing costs is another matter). In this regard, I would say Indiana Jones and the Dial of Destiny under-performed, but it isn't a box office bomb.
But my distinction elides the main point: Why did this movie cost so much to make (same goes for Dead Reckoning Pt. 1). I've seen it said that the pandemic shutdown accounts for this. But what does that mean? I've yet to see an explanation. My guess is this: Contracts were in place where people were guaranteed to get paid, the set for Dial (and other pictures) closes down for several months, and that during all this time people are still getting paid—and then when filming resumes people have to get paid again through extended contracts for the time that was lost during the shutdown. Or something like that.
Does my analysis sound about right? In other words, were it not for Covid, so goes the argument, Indiana Jones and the Dial of Destiny might have had a budget of $150–$200 million. Yes? (And for the record, I liked Dial a lot. It's my third favorite of the five Indy films.)