How do candidates in Europe fund their campaigns? Somebody's giving them money.
Can't speak for other countries, but in the Netherland, all parliamentarians get a fixed salary, currently € 120,000 , from the government, the leaders get an additional amount. The political parties get a government subsidy in line with their size in the chambers, and the parties get annual contribution money from their members, and they can get some donations that need to be disclosed by name of the donator if above € 4,500 (that info is published annually). The total amount of donations, and income from giving courses and such is a modest fraction of the total annual party income.
The reason for the government salary payments and subsidies, is to reduce the risk of perverse incentives.
BTW, everything is taxed (e.g. income-tax) so the amounts are gross amounts, not net.