Why did it happen

I have been thinking lately about the reason I got patellar tendonitis in the first place.
I think it is a combination of factors.

too much jumping in too short a time, I just didn´t give my body the chance to adapt to all the stress that volleyball puts on the knees.

bad technique. probably mostly during the landing phase.

muscle imbalances. Like most athletes i am not particularly strong in the posterior chain.

inflexible, my body is not flexible enough to be able to work during full range of motion.

body weight, i weigh 90 kg, which is not so much for 190 cm, but still gives quite a bit of acceleration to take care of during landing.

explosive power, I have always been more explosive than elastic when it comes to jumping. My standing CMJ is almost the same as a full spike jump. Somehow I think the starting power output gives more of a blow to the knees than an elastic power from the stretch shortening cycle.

Age, I am 45 now, and I am sure that my healing processes work quite a bit slower than they used to...

Science hasn´t found any good reliable indicators as to who actually gets tendonitis and who doesn´t. It seems there are complex mechanisms involved.