Coincidentally they turned out to be incompetent. They obviously aren't trained or "professionals". There has to be a recruitment effort of some sort it seems.
It is not coincidence. That is what happens when you groom and recruit crazy people to do assassinations. They are plausibly deniable as "Lone Wolf"(tm) shooters, but their reliability is very poor. On the other hand, there is a large supply of potential recruits and only one of them needs to get lucky.
Even a failed assassination attempt is effective at dissuading political opponents or impeding their activities.
That is what we are dealing with in the current news events. Four times in a year (yes, there have been at least four attempts by now) is a distinctive pattern.
It is time to go after the sponsors with hammer and tongs. It is also time to go after the supporters. We actually have laws for such activities.