Lower your dbcache. You've set your dbcache to 2000 which would essentially use your entire ram that your RPi has, and I don't think Bitcoin Core will automatically lowers it. The likely case is that some of the UTXOs gets dumped onto the ram fairly quickly and exhausted it. Delete the dbcache configuration or put a more conservative estimate, say 100MB and observe your processes. You can increase it slightly if it doesn't consume all your ram.
Note that the Linux out-of-memory killer is triggered when the combined RAM plus all the swap space (devices and files) are nearly exhausted so assuming Raspbian allocates 2GB of swap, then that means Core must have been using around 3GB, as the OS itself uses 512MB of memory for itself.
If only the RAM is exhausted then naturally, memory pages of processes will start being moved to swap, and as Linux's swap scheduler isn't as efficient as the one in Windows, it's far more likely that your Linux system will just hang when all the RAM is filled because all the CPU cycles are being spent moving pages between bitcoin core from RAM and swap and back again each time Core uses a memory page located in swap.
A dbcache of 500 should leave enough RAM for other processes to breathe with.