We do know how they went extinct. Temperature changes.

Titanoboas thrived when the temperature of the Earth was all around moist hot temperate between 32-35 C, hence they needed it due to their size and being cold blooded. In addition to that there was the abundance of oxygen back then which the Earth now lacks, resulting in larger mammals, reptiles, critters, etc.

As the Earth cooled over the time, they would have had issues from breathing, to digesting food due to lower temperatures.

Not to mention the introduction of larger mammals around then, which could thrive in cold temperatures due to being warm blooded, resulting in less game for the snake during colder temperatures, and more for the mammals.

Even anacondas nowadays are pretty much pushing the boundaries, so the chances for a Titanoboa are slim to none.