Jakob hasn´t LOST at the 2 last WCs in the 1500m. He has won silver. It isn´t a boxing match where there is one winner and one loser. That you ignore his double 5000m gold in the discussion exposes your bias.
Winning the Diamond League isn´t at the same level as winning gold at the WC or Olympics. But it is still a rather good performance.
It has been discussed why Jakob is running almost everything ( not Worlds X country yet).
I think there are at least 3 reasons.
1. He loves to compete but not to train. So he uses every opportunity to skip the boring training.
2. he is like the cannibal Eddy Merckx: He wants to win as much as possible.
3. He knows that nothing sharpens more than racing at this time of the year.
I would like to add something about 3.:
Since some posters here feel uncomfortable when objectiveobserver draws on his own experiences as an elite (veteran) runner I will instead mention a classic example of the past (an example which even Armstrong will appriciate?):
When the internationally completely unknown Peter Snell arrived to the 800m competition of the Rome 1960 OG he had a PB 1:49.2.
There were so many participants that they had to run 2 heats the first day. Semifinal the next day and final the following day. Snell managed to PB every day and famously won the final over the Belgian favorite Moens in 1:46.48. So Snell managed to sharpen quite well with an improvement of 2.72 seconds within 3 days!
An example from the Tokyo OG 2021:
Kerr wasn´t at his best in the heat where he only qualified on time. Racing, however, can sharpen even though you aren´t at your best so he did much better in the semifinal. This time he got a "Q". And in the final the previous sharpeners helped him to a big PR and WON him the bronze.