Utterly unqualified to suggest any causes (wait for the NTSB report on that), but couple compounding factors I've read elsewhere to begin to understand the situation and context:

- Another plane was out of position, grabbing some attention of the controller

- Stop communication was ambiguous about whether talking to previous plane or firetruck

- The colliding plane didn't have "explicit" landing clearance, but a "follow previous plane and land the same way unless told otherwise" implicit landing clearance. In Europe, planes need an explicit landing clearance, the act of granting it may have brought attention to the runway contention. US implicit system (arguably) is a bit more efficient, debate will now be is it worth it (pilots are now required to read back instructions because of past blood... will this result in same thing?)

- This was around midnight and apparently a little foggy, making visual contacts harder

Remember folks, disasters like this are rarely caused by a single factor. NTSB reports are excellent post-mortems that look at all contributing factors and analyze how they compounded into failure. Be human here.

In the USA at controlled airports, aircraft also need explicit landing clearance.

"Jazz 646, number 2, cleared to land 4."

https://youtu.be/Pbm-QJAAzNY?si=h3VEuVNLMf9Z8D1c&t=126

They did have a very explicit clearance.

The controller said “truck 1 stop” that is not ambiguous.