That is your opinion. It is not fact.
Every Candidate who has run for any office does this 3 ways :
(1) raise money while running, using those funds only.
(2) spend their music oney while running , using those funds only.
(3) spend a hybrid of money raised and their own money.
In scenario 2 and 3, the candidates take money out of their own pockets. In these cases, after it is said and done, they will hold fundraisers and events to recoup those expenditures. It happens and it is natural to try and do so.
Running for POTUS, will cost somewhere in the neighborhood of 300M +.
Candidates, win or lose , will hold fund raisers, dinners, give speeches, etc. to pay this off. That is fine, but as you rightly criticize those who get donations on the front end, keep an eye on those who pay on the back end
critizes them as well, if warranted.